[FLINK-36946][Metrics] Optimize sink operator name truncate

[Tartarus0zm]

What is the purpose of the change

Avoid truncation of the Writer/Committer keyword.

Brief change log

• add MetricUtil#truncateOperatorName to optimize Operator name

Verifying this change

• SinkMetricsITCase#testMetrics

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not documented)

[flinkbot]

CI report:

• 6fdd3c3 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[1996fanrui]

Thanks @Tartarus0zm for the optimization!

LGTM assuming CI is green.

[davidradl]

see comments

[Tartarus0zm]

see comments

thanks for your review, I'll update the commit to addressing your concerns.

[Tartarus0zm]

@1996fanrui @davidradl hi, I has updated the commit, take a look again?