fix: add modelgen support for granular read ops

[AaronZyLee]

Description of changes

Added granular modelgen support for Java For the other libraries, the generated code has no problem and only library support is needed

• Android: https://github.com/aws-amplify/amplify-android/pull/2265
• Swift: https://github.com/aws-amplify/amplify-swift/pull/2720
• Flutter: https://github.com/aws-amplify/amplify-flutter/pull/2611
• Doc: https://github.com/aws-amplify/docs/pull/5084

Issue #, if available

https://github.com/aws-amplify/amplify-flutter/issues/2526

Description of how you validated changes

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.

[codecov-commenter]

Codecov Report

Merging #537 (a54ddaa) into main (c6c7b7a) will not change coverage. The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #537   +/-   ##
=======================================
  Coverage   85.69%   85.69%           
=======================================
  Files         148      148           
  Lines        7380     7380           
  Branches     1962     1962           
=======================================
  Hits         6324     6324           
  Misses        959      959           
  Partials       97       97           

Impacted Files	Coverage Δ
...delgen-plugin/src/visitors/appsync-java-visitor.ts	94.80% <ø> (ø)

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