[GOBBLIN-1848] Add tags to dagmanager metrics for extensibility

[Will-Lo]

Dear Gobblin maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following Gobblin JIRA issues and references them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
  • https://issues.apache.org/jira/browse/GOBBLIN-1848

Description

• Here are some details about my PR, including screenshots (if applicable):
  DagManager metrics due to being sent as a gauge in some backend system needs differentiation despite using the same ContextAwareMeter class.

This PR is to add tags (which are extensible) for metric emitting classes to check these tags to process before sending the metrics to their corresponding backend system

Needed to modify DagManagerTests to handle concurrency scenarios where multiple DagManager threads in tests would affect other tests

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.78%. Comparing base (5af6bca) to head (a550c32).
⚠️ Report is 415 commits behind head on master.

Files with missing lines	Patch %	Lines
...ava/org/apache/gobblin/metrics/MetricTagNames.java	0.00%	1 Missing ⚠️
...rvice/modules/orchestration/DagManagerMetrics.java	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3712      +/-   ##
============================================
- Coverage     46.82%   46.78%   -0.05%     
+ Complexity    10804    10791      -13     
============================================
  Files          2141     2143       +2     
  Lines         84429    84524      +95     
  Branches       9383     9392       +9     
============================================
+ Hits          39537    39545       +8     
- Misses        41294    41367      +73     
- Partials       3598     3612      +14     

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