[Java] improve readability of ProxyMethodMapper type

[anuchandy]

This pull request focuses on enhancing the readability of ProxyMethodMapper by refactoring but without altering overall behavior.

• Added ProxyMethod.newBuilder() to ensure immutability.
• Added CollectionUtil, with utility methods to create immutable list/set/map.
• Extracted and simplified the logic that create async and sync response method return type into a utility class - ResponseTypeFactory, so this can be reused across ProxyMethodMapper and ClientMethodMapper.
• Extracted the logic that reads exception configurations from settings in to a standalone type - ExceptionSettingsUtil
• Added ProxyMethodParameterProcessor type responsible for resolving all ProxyMethodParameter, so we can simplify the ProxyMethodMapper internals.
• Added UniqueProxyMethodNameGenerator type so we can isolate the logic that generate unique method names, which again simplifies the ProxyMethodMapper internals.

The auto-rest.java test run for this commit passed the CI - CI run pr

[github-actions]

No changes needing a change description found.

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[weidongxu-microsoft]

LGTM

Any logic change (other than refactor) that you want us pay attention to?

[anuchandy]

LGTM

Any logic change (other than refactor) that you want us pay attention to?

Thanks, Weidong. There are a few conditions that have been inverted to improve readability, If you could skim over it.. the types are ResponseTypeFactory, and ProxyMethodParameterProcessor, to the best of my knowledge, this should not alter any expected behavior.

[XiaofeiCao]

LGTM, thanks!