Cache the value of `changed_attributes` when calling `changes_applied`

`changes_applied` calles `changes`, which will call `changed_attributes`
multiple times in a loop. This method actually performs work now, so we
should cache the results while looping over it when we know it cannot
change.
Update documentation to match change in #5942 [ci skip]
Speed up JRuby tests by improving its startup time

Emulate `jruby --dev` which improves JRuby's startup time.

See
https://github.com/jruby/jruby/wiki/Improving-startup-time#use-the---dev-flag

Follow @headius' idea and give Java more memory to reduce GC time.
Merge pull request #16646 from sgrif/sg-perf-regression

Cache the value of `changed_attributes` when calling `changes_applied`
[ci skip] Added documentation for has_and_belongs_to_many extension parameter
Merge pull request #16697 from tomkadwill/has_and_belongs_to_many_documenting_extension_param

[ci skip] Added documentation for has_and_belongs_to_many extension parameter
[ActiveJob] Autoload adapters
Keep the first string we fetch

Otherwise, it's possible for GC to run in between, and fail the test.
Merge pull request #16613 from splattael/master

Speed up JRuby tests by improving the startup time
Merge pull request #16700 from seuros/autoload

[ActiveJob] Autoload adapters
[ci skip] Updated documentation syntax of block parameter for rdoc
Merge pull request #16703 from tomkadwill/documented_any_block_param

[ci skip] Updated documentation syntax of block parameter for rdoc
[ci skip] Updated documentation syntax of block parameter for rdoc
[ci skip] Updated include to reference record parameter for rdoc
Merge pull request #16706 from tomkadwill/documented_include_record_param

[ci skip] Updated include to reference record parameter for rdoc
Merge pull request #16705 from tomkadwill/documented_many_block_param

[ci skip] Updated documentation syntax of block parameter for rdoc
Adjusted punctuation and grammar for Form Helpers guide [ci skip]
Merge pull request #16708 from zzak/bcjordan-patch-1

Adjusted punctuation and grammar for Form Helpers guide [ci skip]
[ci skip] Updated documentation syntax of other parameter for rdoc
Merge pull request #16713 from tomkadwill/documented_eqls_other_param

[ci skip] Updated documentation syntax of other parameter for rdoc