[to #556] metrics: attach cluster label to metrics (#558)

[ti-srebot]

cherry-pick #558 to release-3.1
You can switch your code base to this Pull Request by using git-extras:

# In client-java repo:
git pr https://github.com/tikv/client-java/pull/579

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/client-java.git pr/579:release-3.1-6cbf56aede70

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Signed-off-by: iosmanthus myosmanthustree@gmail.com

What problem does this PR solve?

Issue Number: to #556

Problem Description:

• code change for client-java
• code change for grafana panel

Add cluster label for metrics in client-java with the value of cluster id.

• Need to cherry-pick to the release branch

[ti-srebot]

/run-all-tests

[zz-jason]

LGTM

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-3.1@c2b23db). Click here to learn what that means.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             release-3.1     #579   +/-   ##
==============================================
  Coverage               ?   30.14%           
  Complexity             ?     1168           
==============================================
  Files                  ?      263           
  Lines                  ?    16639           
  Branches               ?     1897           
==============================================
  Hits                   ?     5015           
  Misses                 ?    11066           
  Partials               ?      558           

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[zz-jason]

LGTM