feat: Add ModelIdentifier for all Java models

[tylerjroach]

Description of changes

If CPK flag is enabled:

• We will now create a T: ModelIdentifier for all models (not just cpk with sort keys)
• resolveIdentifier will only return the ModelIdentifier if cpk + sort key
• deprecation warning for resolveIdentifier as it is only intended to be used internally in Amplify

All changes are additive (non-breaking)

Description of how you validated changes

• Added snapshot tests for new scenarios

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• Breaking changes to existing customers are released behind a feature flag or major version update
• Changes are tested using sample applications for all relevant platforms (iOS/android/flutter/Javascript) that use the feature added/modified

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[tylerjroach]

Marking as draft until improvements are fully staged in Amplify Android.

[codecov-commenter]

Codecov Report

Merging #612 (3865fb8) into main (21bbff8) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main     #612      +/-   ##
==========================================
- Coverage   85.92%   85.91%   -0.01%     
==========================================
  Files         152      152              
  Lines        7493     7492       -1     
  Branches     1959     1958       -1     
==========================================
- Hits         6438     6437       -1     
  Misses        962      962              
  Partials       93       93              

Impacted Files	Coverage Δ
...delgen-plugin/src/visitors/appsync-java-visitor.ts	94.79% <100.00%> (-0.02%)	⬇️

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[manueliglesias]

LGTM 👍