fix(auth): add sub and identities as standard attributes

[Jordan-Nelson]

Issue #, if available:

Description of changes:

• Add sub and identities attributes

This is a subset of the changes that went into next in #1768 and #1804. I did not include the rest of the changes since the changes to the parse constructor is breaking.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #1825 (05b673d) into main (6a5fdfc) will increase coverage by 0.34%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1825      +/-   ##
==========================================
+ Coverage   42.14%   42.48%   +0.34%     
==========================================
  Files         371      375       +4     
  Lines       10768    10870     +102     
==========================================
+ Hits         4538     4618      +80     
- Misses       6230     6252      +22     

Flag	Coverage Δ
android-unit-tests	∅ <ø> (∅)
flutter-unit-tests	31.45% <ø> (ø)
ios-unit-tests	89.04% <ø> (-0.55%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...pes/auth/attribute/cognito_user_attribute_key.dart	50.00% <ø> (ø)
...e/ios/unit_tests/MockAnalyticsCategoryPlugin.swift	15.38% <0.00%> (ø)
...y_flutter_ios/example/ios/Runner/AppDelegate.swift	0.00% <0.00%> (ø)
.../ios/unit_tests/amplify_flutter_exampleTests.swift	94.59% <0.00%> (ø)
...ios/example/ios/unit_tests/AtomicResultTests.swift	87.75% <0.00%> (ø)