Use SQL COUNT and LIMIT 1 queries for none? and one? methods if no block or limit is given,
instead of loading the entire collection to memory. The any? and many? methods already
follow this behavior.

[Eugene Gilburg & Rafael Mendonça França]

The cache name should be converted to a string when given, not compared
as a symbol. This edge case is already adequately covered by our tests,
but was masked by another issue where we were incorrectly updating the
counter cache twice. When paired with a bug where we didn't update the
counter cache because we couldn't find a match with the name, this made
it look like everything was working fine.

Fixes #10865.

Remaining are `limit`, `precision`, `scale`, and `type` (the symbol
version). These will remain on the column, since they mirror the options
to the `column` method in the schema definition DSL

Fixes #18696.

`bound_attributes` is now used universally across the board, removing
the need for the conversion layer. These changes are mostly mechanical,
with the exception of the log subscriber. Additional, we had to
implement `hash` on the attribute objects, so they could be used as a
key for query caching.

The column is primarily used for type casting, which we're trying to
separate from the idea of a column. Since what we really need is the
combination of a name, type, and value, let's use the object that we
already have to represent that concept, rather than this tuple. No
consumers of the bind values have been changed, only the producers
(outside of tests which care too much about internals). This is
*finally* possible since the bind values are now produced from a
reasonable number of lcoations.

I'm going to be extracting this logic into a clause class, things need
to go through a method and not access the values hash directly.

This removes the need to duplicate much of the logic in `WhereClause`
and `PredicateBuilder`, simplifies the code, removes the need for the
connection adapter to be continuously passed around, and removes one
place that cares about the internal representation of `bind_values`

Part of the larger refactoring to change how binds are represented
internally

[Sean Griffin & anthonynavarre]

When we made sure that the counter gets updated in memory, we only did
it on the has many side. The has many side only does the update if the
belongs to cannot. The belongs to side was updated to update the counter
cache (if it is able). This means that we need to check if the
belongs_to is able to update in memory on the has_many side.

We also found an inconsistency where the reflection names were used to
grab the association which should update the counter cache. Since
reflection names are now strings, this means it was using a different
instance than the one which would have the inverse instance set.

Fixes #18689

[Sean Griffin & anthonynavarre]

There are many ways that things end up getting passed to `concat`. Not
all of those entry points called `flatten` on their input. It seems that
just about every method that is meant to take a single record, or that
splats its input, is meant to also take an array. `concat` is the
earliest point that is common to all of the methods which add records to
the association. Partially fixes #18689

Bind values are no longer a thing, so this is unnecessary.

See 4d7a6229 for the reasoning

The structure of `values[:where]` is going to change, with an
intermediate definition of `where_values` to aid the refactoring.
Accessing `values[:where]` directly messes with that, signficantly.

The array wrapping is no longer necessary, since `where_values` will
always return an array.

Specifically, the issue is relying on `where_unscoping` mutating the
where values. It does not, however, mutate the bind values, which could
cause an error under certain circumstances. This was not exposed by the
tests, since the only place which would have been affected is unscoping
a boolean, which doesn't go through prepared statements. I had a hard
time getting better test coverage to demonstrate the issue.

This in turn, caused `merge` to go through proper logic, and try to
clear out the binds associated with the unscoped relation, which then
exposed a source of `nil` for the columns, as binds weren't expanding
`{ "posts.id" => 1 }` to `{ "posts" => { "id" => 1 } }`. This has been
fixed.

The bulk of `create_binds` needed to be moved to a separate method,
since the dot notation should not be expanded recursively.

I'm pretty sure this removes a subtle quirk that a ton of code in
`Relation::Merger` is working around, and I suspect that code can be
greatly simplified. However, unraveling that rats nest is no small task.

These requires were added only to change deprecation message

This reverts commit ae96f229.

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/attribute_methods.rb

Before this commit, returning `false` in an ActiveRecord `before_` callback
such as `before_create` would halt the callback chain.

After this commit, the behavior is deprecated: will still work until
the next release of Rails but will also display a deprecation warning.

The preferred way to halt a callback chain is to explicitly `throw(:abort)`.

Add missing nodoc's
Change `assoc_klass` argument name to `association_klass`
Change `prev_reflection` argument name to `previous_reflection`
Change `prev` to `previous_reflection` in `#get_chain`
Switch use of `refl` and `reflection` in `#get_chain` so main parameter
is not abbreviated.
Add missing space in `#add_constraints`

This moves the `#type_caster` from the `aliased_table_for` and into the
initialize of the `alias_tracker`.

`yield` instead of relying on checking if the reflection is equal to the
`chain_head`.

Instead of initializing an empty connection use the base table name
instead. Split up and refactor `#create` to be 2 methods `#create` and
`#create_with_joins`. Removes the need to update the count by 1 on
initialzing a JoinDependency.

This moves `alias_candidate` out of the `ReflectionProxy` and into the
`AbstractReflection` so it is shared by all reflections. Change
`alias_name` to a method and and remove assignment in `#get_chain`.

After the refactorings we're only using the connection and not the alias
tracker anymore. This builds on commit 18019.

Reuse the already available `@connection` to reduce the surface area of
the alias tracker's API. We can then remove the `attr_reader` because
the connection is already available.

This makes the `#alias_name` more functional.

Move `RuntimeReflection` and `PolymorphicReflect` into Reflection. This
allows the methods to inherit from `ThroughReflection` and DRY up the
methods by removing duplicates.

The linked list lets us use a loop in `#add_constraints` and completely
remove the need for indexing the iteration becasue we have access to the
next item in the chain.

By concatnating the `ReflectionProxy` with the `chain` we remove
the need for `#construct_tables` because the `chain` is now in the
correct order (order of the chain DOES matter).

Putting the `#alias_name` into ReflectionProxy means we don't have to
cache the `#alias_name` globally anymore - it's not cached per query.

`is_first_chain`, `items` and `klass` are no longer beneficial and can
be called directly instead of via their assignments - because they are
each only used once.

Move method structure into reflection classes for accessibly on each
reflection rather than by traversing the chain.

The `RuntimeReflection` class allows the reflection to be accessed at
runtime - then we always know which reflection we are accessing in the
chain. The `#get_chain` method then allows us to recursively access the
chain through the `RuntimeReflection`.

`#constraints` builds a flattened version of `scope_chain` to
allow it to be accessible without requiring an index when iterating
over the `scope_chain`

Fixes #18237