Fixes #9275.

When `#order` is called with a Symbol this patch will prepend the quoted_table_name.
Before the postgresql adapter failed to build queries containg a join and an order
with a symbol.

This expansion happens for all adapters.

Taking the wise advice of @carlosantoniodasilva

The function is now called has_arguments? so that it's easier to tell
that it's just checking to see if the args are blank or not.

for query methods in a where_clause. Also, modified the CHANGELOG entry
because it had false information and added tests.

* Fix example queries
* Remove doc entries of where.like/not_like.
* Remove :chain from where.not related docs. To me that's an implementation
  detail and we don't expect people to use where(:chain).not.

The real win with these chain methods is where.not, that takes care of
different scenarios in a graceful way, for instance when the given value
is nil.

    where("author.id != ?", author_to_ignore.id)
    where.not("author.id", author_to_ignore.id)

Both where.like and where.not_like compared to the SQL versions doesn't
seem to give us that much:

    Post.where("title LIKE 'ruby on%'")
    Post.where.like(title: 'ruby on%'")
    Post.where("title NOT LIKE 'ruby on%'")
    Post.where.not_like(title: 'ruby on%'")

Thus Rails is adding where.not, but not where.like/not_like and others.

This commit stems from https://github.com/rails/rails/pull/8332#issuecomment-11127957

Since the formats in which conditions can be passed to `not` differ
from the formats in which conditions can be passed to `like` and `not_like`,
then I think it's worth adding rdoc and tests to show this behavior

Arel::Nodes::In inherits from Arel::Nodes::Equality, so the case
statement was always using the Equality operator for both scenarios,
resulting in a not equal query instead.

This commit updates the rdoc of AR#where to match the changes applied
in https://github.com/rails/rails/commit/6ba0f97 that is:

* `where(nil)` has the same effect of `where('')`: a no op
* `where` (no args) has the same effect of `where(:chain)`: to create a WhereChain

Consider this scenario:

    if params[:foo]
      conditions = { foo: true }
    end

    foos = Foo.where(conditions).order(:id)

When params[:foo] is nil, this would call:

    foos = Foo.where(nil).order(:id)

In this scenario, we want Foo.where(conditions) to be the same as calling
Foo.all, otherwise we'd get a "NoMethodError order for WhereChain".

Related to #8332.

These are for internal use only and cannot be relied on as part of the
public API. See discussion on 8c2c6051.

examples:

  Model.where.not field: nil
  #=> "SELECT * FROM models WHERE field IS NOT NULL

  Model.where.like name: 'Jeremy%'
  #=> "SELECT * FROM models WHERE name LIKE 'Jeremy%'

this feature was originally suggested by Jeremy Kemper https://github.com/rails/rails/pull/5950#issuecomment-5591330

Closes #5950

allocations

Before:

Calculating -------------------------------------
                  ar        87 i/100ms
-------------------------------------------------
                  ar      823.4 (±11.8%) i/s -       4089 in   5.070234s

After:

Calculating -------------------------------------
                  ar        88 i/100ms
-------------------------------------------------
                  ar      894.1 (±3.9%) i/s -       4488 in   5.028161s

Same test as 3a6dfca7

This reverts commit abf8de85.
We should take a deeper look to those cases flat_map doesn't do deep
flattening.

irb(main):002:0> [[[1,3], [1,2]]].map{|i| i}.flatten
=> [1, 3, 1, 2]
irb(main):003:0> [[[1,3], [1,2]]].flat_map{|i| i}
=> [[1, 3], [1, 2]]

In some circumstances engine was Arel::Table.engine which for separate
reasons was an ActiveRecord::Model::DeprecationProxy, which caused a
deprecation warning.

In any case, we want the actual model class here, since we want to use
it to infer information about associations.

Allows you to specify the model association key in a belongs_to
relationship instead of the foreign key.

The following queries are now equivalent:

Post.where(:author_id => Author.first)
Post.where(:author => Author.first)

PriceEstimate.where(:estimate_of_type => 'Treasure', :estimate_of_id => treasure)
PriceEstimate.where(:estimate_of => treasure)

This is a cleaner version of #6916.

Closes #3165.

    User.order("name asc").order("created_at desc")
    # SELECT * FROM users ORDER BY created_at desc, name asc

This also affects order defined in `default_scope` or any kind of associations.

This reverts commit 14fc8b34.

Reason: we need to discuss a better path from this removal.

Conflicts:
	activerecord/lib/active_record/reflection.rb
	activerecord/test/cases/base_test.rb
	activerecord/test/models/developer.rb

It doesn't serve much purpose now that ActiveRecord::Base.all returns a
Relation.

The code is moved to active_record_deprecated_finders.