Fix `Message::Encryptor` default cipher [ci skip]

Follow up of #29263

[ Assain Jaleel & Kasper Timm Hansen ]

Default Message Encryptor Cipher to AES-256-GCM From AES-256-CBC

- Introduce a method to select default cipher, and maintain backward compatibility

Generate field ids in `collection_check_boxes` and `collection_radio_buttons`

Document Module#delegate_missing_to in the guides [ci skip]

Added a small section for it in the `Active Support Core Extensions`
guide. [ci skip]

Fix the mistake of not using Ruby's ENV hash from the get go and get
windows support.

This makes sure that the labels are linked up with the fields.
Fixes #29014

No need to pass `#cleanup` options through to `LocalCache#clear`.

Fixes #29081. References #25628.

See https://github.com/rails/rails/issues/29067#issuecomment-301342084
for rationale.

This reverts commit b76f82d7.

Fixes #29067. Fixes #29081.

Remove `null_allowed` option from doc [ci skip]

This option was added in b9fa3541. But it does not seem to work.

Split up the caching tests as prep for adding a new cache store. Slices
the mega test/caching_test.rb into behavior modules, concrete store
tests, and cross-cutting store tests.

Considering moving cache store behavior modules into lib/ so they may be
used for acceptance testing by third parties.

[ci skip] Add backquote to :counter_cache option

Ensure MSSQL password uses real ENV var.

[ci skip] Fix another link in active_record_postgresql.md

Fix link in active_record_postgresql.md [ci skip]

remove the extra comma in association_basics.md [ci skip]

That won't be true for Action Pack and Action Mailer.

Bundle capybara 2.14.1 that includes fix for Ruby warnings

Ref: https://github.com/teamcapybara/capybara/pull/1868

Remove unreachable code

`Time.find_zone!` raise `ArgumentError` if invalid value is specified.
https://github.com/rails/rails/blob/379a0b42daf0d8e14130db7fd886d05d8d88e3f2/activesupport/lib/active_support/core_ext/time/zones.rb#L97..L99

Therefore, the return value never becomes nil.

form_with requires people to pass an id manually, so users can just
prefix their namespace right there.

Forgot all about https://github.com/rails/rails/pull/28844/files#r113780934

cc @rafaelfranca

Rails.cache.write_multi foo: 'bar', baz: 'qux'

Plus faster `fetch_multi` with stores that implement `write_multi_entries`.
Keys that aren't found may be written to the cache store in one shot
instead of separate writes.

The default implementation simply calls `write_entry` for each entry.
Stores may override if they're capable of one-shot bulk writes, like
Redis `MSET`.

Update upgrading guide w.r.t. Parameters to use other example method …

Update upgrading guide w.r.t. Parameters to use other example method than slice as this has actually been implemented by Parameters

PostgreSQL 10 converts unknown type to text type