make `db:structure:load` listed with `rake -T`
Typo, grammar and textual changes [ci skip]
docs, restructure newly added part to `includes`. [ci skip]

This is a follow up to #14139.

/cc @carlosantoniodasilva
Merge pull request #14952 from gregmolnar/schema_load

make `db:structure:load` listed with `rake -T`
Refactor test to not care about the specific result of valid?

Only care about its truthiness rather than asserting specific true/false
values. If we need to check for the return value in particular, there will
be a test for that.
Remove duplicated fixture addition
Reorganize ActiveRecord tasks [Arun Agrawal & Abd ar-Rahman Hamidi]
Merge pull request #14940 from arunagw/hbakhtiyor-test-db-namespaces-ar

Reorganize ActiveRecord's rake tasks
Revert "Merge pull request #14940 from arunagw/hbakhtiyor-test-db-namespaces-ar"

This reverts commit fe9859600824268ff614cb3eb48b62c7165a1fbd, reversing
changes made to add9560643ef79830febf47fa1228752d1df3502.
Remove tests method for test cases when controller can be inferred.
Merge pull request #14959 from akshay-vishnoi/doc_changes

Typo, grammar and textual changes [ci skip]
Merge pull request #14966 from tgxworld/remove_unnecessary_setting_of_controller_name

Remove tests method for test cases when controller can be inferred.
refactor, move `column_for` to `AbstractAdapter` for better reuse.
Document ActionController::TestCase::Behavior#process

[ci skip]
Merge pull request #14923 from gaurish/document-testcase-process

Document ActionController::TestCase::Behavior#process

[ci skip]
Rails One Click is not maintained anymore [ci skip]

Let's tell people that they should rely on Tokaido instead of Rails One
Click.

Fixes #14960.
Convert column name to string only once
Simplify unless conditional with OR
Get rid of conditional since column_for handles raising now

column_for will raise in case column is not found for the given table,
so there is no need to handle that here.
Simplify building options hash in rename column method for mysql