HDDS-10215. Speed up some tests that use OmTestManagers

[adoroszlai]

What changes were proposed in this pull request?

Some of the slowest unit tests use OmTestManagers to launch OM. It takes ~10 seconds to initialize (half of that is Ratis leader election). The test cases are pretty quick after that.

[INFO] Tests run: 12, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 148.9 s -- in org.apache.hadoop.ozone.om.service.TestOpenKeyCleanupService
[INFO] Tests run: 11, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 133.0 s -- in org.apache.hadoop.ozone.om.TestBucketManagerImpl
[INFO] Tests run: 9, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 108.3 s -- in org.apache.hadoop.ozone.om.TestKeyManagerUnit
[INFO] Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 83.42 s -- in org.apache.hadoop.ozone.om.TestOmSnapshotManager

This change speeds up four of these tests, mostly by converting per-method setup to per-class, to reduce the overhead.

Also, wait for OM leader election before proceeding with the test, to avoid an exception related to failover retry while trying to create the RPC client.

Use test method name as volume name to avoid conflicts, and unexpected number of buckets/keys.

Some of the assertions need to be tweaked to account for objects left over and operations performed by other test cases.

https://issues.apache.org/jira/browse/HDDS-10215

How was this patch tested?

[INFO] Tests run: 12, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 20.262 s - in org.apache.hadoop.ozone.om.service.TestOpenKeyCleanupService
[INFO] Tests run: 11, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 15.457 s - in org.apache.hadoop.ozone.om.TestBucketManagerImpl
[INFO] Tests run: 9, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 15.444 s - in org.apache.hadoop.ozone.om.TestKeyManagerUnit
[INFO] Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 14.75 s - in org.apache.hadoop.ozone.om.TestOmSnapshotManager

https://github.com/adoroszlai/ozone/actions/runs/7670459056/job/20907076486

[sodonnel]

LGTM. This should speed up every test run by a few minutes which is very nice.

[adoroszlai]

Thanks @sodonnel for the review.