Simplify rake test vs rake test:all

Renames `rake test:all` to `rake test` by changing old `rake test:run` to previous version of `rake test:all`.  Removes old definition of `rake test`. Also renames `rake test:all:db` to `rake test:db` and deprecates `rake test:all` & `rake test:all:db`
Fix Rails::Paths::Path.unshift interface
Merge pull request #17348 from DavidGeukers/rake_test_all

simplify rake test vs rake test:all
Follow the coding conventions
Merge pull request #17596 from aderyabin/follow_convension

Follow the coding conventions
Merge pull request #17593 from igas/paths-unshift-arity

Fix Rails::Paths::Path.unshift interface
Improve railties changelog entry and move latest to the top [ci skip]
Abstract encoding strategy for ActiveSupport::MessageVerifier
Merge pull request #17604 from rymohr/message-verifier-case-sensitivity

Abstract encoding strategy for ActiveSupport::MessageVerifier
[ci skip] Add one more example to routing testing, and highlight association
name keywords
Merge branch 'sandipransing-master'
[ci skip] Capybara added to other testing approaches
Merge pull request #17612 from sandipransing/testing-guide

[ci skip] Capybara added to other testing approaches
[ci skip] Improve upon testing tasks guide

Add missing testing tasks and also improve upon tasks descriptions
Merge pull request #17613 from sandipransing/testing-guide

[ci skip] Improve upon testing tasks guide
Add basic tests for ActionDispatch::ExceptionWrapper
exec_prepared is GVL friendly, so lets use it.

also increase the version of pg required so that people will get the
GVL friendly version
[ci skip] Remove deprecated testing tasks

This has changed recently and so rake test:all and rake
test:all:db are deprecated.
Merge pull request #17618 from sandipransing/testing-guide

[ci skip] Remove deprecated testing tasks
[CI SKIP] Corrections to testing guide.

Partially revert https://github.com/rails/rails/commit/c31e638a37946a120f6dbf207127d36beea5ab85.