We have several test cases on "tricky" types that are essentially
testing that `update_all` goes through the same type casting behavior as
a normal assignment + save. We recently had another case to add this
test for another type in https://github.com/rails/rails/pull/12742.

Rather than testing this separately for every type which is "tricky"
when round tripping, let's instead have a fairly exhaustive test that
ensures we're getting the correct values at every step for `update_all`.
Given the structure of the code now, we can be confident that if the
type is correct, and `update_all` is type casting correctly, we're going
to get the right behavior for all types.

Also takes a step towards supporting types which use a character other
than ',' for the delimiter (`box` is the only built in type for which
this is the case)

If we want to have type decorators mess with the attribute, but not the
column, we need to stop type casting on the column. Where possible, we
changed the tests to test the value of `column_defaults`, which is
public API. `Column#default` is not.

HStore columns come back from the database separated by a comma and a
space, not just a comma. We need to mirror that behavior since we
compare the two values.

Also adds a regression test against JSON to ensure we don't have the
same bug there.

We have several mutable types on Active Record now. (Serialized, JSON,
HStore). We need to be able to detect if these have been modified in
place.

There's a lot more that can be moved to these, but this felt like a good
place to introduce the object. Plans are:

- Remove all knowledge of type casting from the columns, beyond a
  reference to the cast_type
- Move type_cast_for_database to these objects
- Potentially make them mutable, introduce a state machine, and have
  dirty checking handled here as well
- Move `attribute`, `decorate_attribute`, and anything else that
  modifies types to mess with this object, not the columns hash
- Introduce a collection object to manage these, reduce allocations, and
  not require serializing the types

We guarantee that `model.value` does not change after
`model.save && model.reload`. This requires type casting user input for
non-string types.

```
activerecord/test/cases/adapters/postgresql/range_test.rb:159: warning: (...) interpreted as grouped expression
activerecord/test/cases/finder_test.rb:38: warning: shadowing outer local variable - e
activerecord/test/cases/finder_test.rb:43: warning: shadowing outer local variable - e
```

In some cases there is a difference between the two, we should always
be doing one or the other. For convenience, `type_cast` is still a
private method on type, so new types that do not need different behavior
don't need to implement two methods, but it has been moved to private so
it cannot be used accidentally.

- The following is now true for all types, all the time
  - `model.attribute_before_type_cast == given_value`
  - `model.attribute == model.save_and_reload.attribute`
  - `model.attribute == model.dup.attribute`
  - `model.attribute == YAML.load(YAML.dump(model)).attribute`
- Removes the remaining types implementing `type_cast_for_write`
- Simplifies the implementation of time zone aware attributes
- Brings tz aware attributes closer to being implemented as an attribute
  decorator
- Adds additional point of control for custom types

`serialize` is now lazy, so the workaround is no longer needed.

The times would be equivalent, even if they were in different time
zones. E.g. 12:00 UTC == 5:00 PDT

Millisecond inequality causes failures on Travis

This adds a regression test for #14411, which was fixed by #15503.

Closes #14411
Closes #14595

BC era year is (astronomical year + 1) and starts from 1 BC.

`@raw_attributes` should not contain the type-cast, mutable version of
the value.

Revert "test pg, remove unused column assignments. Follow up to 254cdf47"

Related to #15492

This reverts commit 254cdf47.
This reverts commit 4bcf9029.

There are public methods that assume `Column#default` is type casted.
The return value of `Column#default` is publicly relevant and should not change.

/cc @sgrif

That data is internal to Active Record. What we care about is that
new records have the right default value.

/cc @sgrif

Nearly completely implemented in terms of custom properties.
`_before_type_cast` now stores the raw serialized string consistently,
which removes the need to keep track of "state". The following is now
consistently true:

- `model.serialized == model.reload.serialized`
- A model can be dumped and loaded infinitely without changing
- A model can be saved and reloaded infinitely without changing

This is an intermediate solution. It is related to the refactoring @sgrif
is making and will change in the future.

MySQL and PostgreSQL provide a column type override in order to properly
type cast computed columns included in a result set. This should never
override the known types of full fledged columns. In addition to messing
up computed properties, this would have led to inconsistent behavior
between a record created with `new`, and a record created with `last` on
the mysql adapter in the following cases:

- `tinyint(1)` with `emulate_booleans` set to `false`
- `text`, `string`, `binary`, and `decimal` columns

The solution presented in this patch is not efficient. We should replace it
in the near future. The following needs to be worked out:
  * Is `@attributes` storing the Ruby or SQL representation?
  * `cacheable_column?` is broken but `hstore` and `json` rely on that behavior

Refs #15369.

/cc @sgrif @rafaelfranca