Cache auth scheme resolution - #7282

Motivation and Context

Cache deterministic auth scheme resolution results to reduce per-request CPU overhead. Auth scheme resolution is called on every request and produces the same result for a given set of inputs when using the default provider - caching avoids repeated allocation and computation.

Modifications

• Generate ConcurrentHashMap<String, List<AuthSchemeOption>> authSchemeCache field on sync/async client classes
• Cache activates only when: 1) no per-request auth scheme provider override AND 2) client-level provider instanceof DefaultXxxAuthSchemeProvider
• Disabled for endpoint-based auth provider services (e.g. S3) where resolution depends on dynamic endpoint parameters
• Cache key composition varies by service characteristics:
  • Uniform-auth + sigv4: region
  • Uniform-auth + sigv4a: region + ":" + regionSet
  • Per-op-auth + sigv4: operationName + ":" + region
  • Per-op-auth + sigv4a: operationName + ":" + region + ":" + regionSet

Testing

• Added unit tests
• Ran benchmarks confirming no regression on full-roundtrip workloads and significant savings on the isolated auth resolution path

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license