Add additional checksum algorithms

[zoewangg]

Motivation and Context

Add support for additional checksum algorithms: XXHASH64, XXHASH3, XXHASH128, SHA512, and MD5. Note that this change will be merged to a feature branch first

• The XXHASH algorithms require the AWS CRT library.
• MD5 is not supported for flexible checksums (httpChecksum trait). MD5 can only be used when a pre-calculated MD5 header is provided. Attempting to specify MD5 as the checksum algorithm throws IllegalArgumentException.
• MD5 response validation is skipped in HttpChecksumUtils.shouldSkipAlgorithm() since MD5 is not a valid flexible checksum algorithm

Modifications

• Added new checksum algorithm constants in DefaultChecksumAlgorithm: XXHASH64, XXHASH3, XXHASH128
• Added business metrics for new checksum algorithms in BusinessMetricFeatureId and BusinessMetricsUtils
• Changed aws-crt dependency from test scope to optional for runtime CRT checksum support

Testing

• Added XxHashChecksumTest for XXHASH algorithm variants
• Added XxHashNotAvailableTest to verify graceful handling when CRT is unavailable
• Added tests for business metrics verification
• Updated existing checksum tests to cover new algorithms

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

[zoewangg]

The priority order is pending on perf tests