Add support for StringSet metric in Java SDK to track set of unique s… #28509

Job	Run time
Check environment variables	11s
Build python source distribution	1m 46s
Build python wheels on auto for ubuntu-latest	55m 22s
Prepare GCS	0s
Build python wheels on auto for macos-13	2m 59s
Build python wheels on auto for windows-latest	4m 57s
Build python wheels on aarch64 for ubuntu-latest	24m 0s
Upload python source distribution to GCS bucket	0s
Branch repo nightly	0s
Upload wheels to GCS bucket	0s
List files on Google Cloud Storage Bucket	0s
	1h 29m 15s

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