Preparing for 4.2.0.beta1 release
Use system /tmp when testing actionpack

https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
added support and enabled parallel execution of the actionpack tests.

However it introduced https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
since one cannot connect to a socket file that's inside a Vagrant synced folder
due to security restrictions, and DRb tries to.

Also rename the temporary files to make it obvious that they're rails-related,
since now they're placed outside the project's directory.

Fixes https://github.com/rails/rails/commit/c64bff2c87ebf363703c63ecd4a96d56a1a78364
Update documentation to match change in #5942 [ci skip]
Don't ignore constraints in redirect routes

https://github.com/rails/rails/commit/402c2af55053c2f29319091ad21fd6fa6b90ee89
introduced a regression that caused any constraints added to redirect routes
to be ignored.

Fixes #16605
use self instead of #read_attribute
[ci skip] Modify a web-console PR link
Merge pull request #16715 from y-yagi/update_4_2_release_notes

[ci skip] Modify a web-console PR link for release noted
Use less iterations for KeyGenerator in tests

This commit improves performance of cookie tests:

Ruby  |   After  |   Before
----- | --------:| --------:
MRI   |    5.03s |     9.28s
JRuby |   25.45s |  1648.23s

Please note the improvement for JRuby.
Merge pull request #16661 from edogawaconan/doc-fix

Update documentation to match change in #5942 [ci skip]
minor changelog formatting changes.
fix broken `gem` method with non-String arguments. Closes #16709.

This was caused by #15327.
Fix spelling. [CI SKIP]
Merge pull request #16719 from tgxworld/fix_spelling_in_changelog

Fix spelling. [CI SKIP]
Correctly detect mutation on serialized columns mapping to binary

Fixes #16701
[ci skip] Update 4_2_release notes
[ci skip] Fix typo of `collection_singular_ids=` method.
[ci skip] Fix typo of `collection=` method.
Merge pull request #16721 from yui-knk/fix/guides_association_basics

[ci skip] Fix typo of `collection=` method.
Merge pull request #16722 from yui-knk/fix/guides_association_basics2

[ci skip] Fix typo of `collection_singular_ids=` method.
Merge pull request #16702 from sgrif/sg-binary-serialized

Correctly detect mutation on serialized columns mapping to binary