Avoid extra scoping in delegating to klass methods in the `scope` block

Use MethodCallAssertions instead of Mocha#expects

Since #29301, delegating to klass methods in the `scope` block would
cause extra scoping by the receiver itself. The extra scoping would
always override intermediate scoping like `unscoped` and caused the
regression #33387. To keep the original scoping behavior, should avoid
the extra scoping in the `scope` block.

Fixes #33387.

#33363 has two regressions. First one is that `insert_fixtures_set` is
failed if flags is an array. Second one is that connection flags are not
restored if `set_server_option` is not supported.

Link to the corresponding ActiveStorage::Blob methods, whose docs more accurately describe their effects. [ci skip]

Many calls to `Mocha#expects` preceded the introduction of
`ActiveSupport::Testing::MethodCallAssertions` in 53f64c0f,
and many are simple to replace with `MethodCallAssertions`.

This patch makes all these simple replacements.

Step 5 in #33162

This reverts commit eb807384.

If the current scope is affected by the `unscoped` block, `all` won't be
the same with `spawn`.

 [ci skip]  Add situation for belongs to association.

use set_server_option if possible

Revert "Merge pull request #33385 from lanzhiheng/add-example-for-has-and-belongs-to-many-association"

This reverts commit 3c8c4100, reversing
changes made to daee94da.

We have this information below in the reference section for
has_and_belongs_to_many.

Fix issue with `button_to`'s `to_form_params`

 [ci skip]  Add example for `has-and-belongs-to-many` association.

Normalize the date component to 2000-01-01 automatically

Remove/Replace some more calls to Mocha#stubs

Also?
Updated failing test.

(cherry picked from commit da34d4766c33a042aeb92778a492fa810ec23001)

Missed these in preparing #33337

Should have been removed in #33309.

`button_to` was throwing exception when invoked with `params` hash that
contains symbol and string keys. The reason for the exception was that
`to_form_params` was comparing the given symbol and string keys.

The issue is fixed by turning all keys to strings inside
`to_form_params` before comparing them.

Clarify test cases

 Modify the expression's issue for `errors.add` document.

[ci skip]

Closes #32193.

Remove extra stub of `ActiveRecord::Base::connection` in
`activerecord/test/cases/tasks/mysql_rake_test.rb`.

Remove extra stub of `File::exist?` in
`activerecord/test/cases/tasks/sqlite_rake_test.rb`.

`ActiveRecord::Base::establish_connection` shouldn't return `true`
in test cases.

Related to https://github.com/rails/rails/pull/33337.

Stub with minitest not mocha

fix test_should_impose_childless_html_tags_in_html failure with JRuby

Merge pull request #33365 from lanzhiheng/fix-document-issue-about-active-record-callbacks-after_touch

 Fix document issue in active record callback about `after_touch` hook.

[ci skip]