[GOBBLIN-2194] Close temporal metrics scope on job completion

[abhishekmjain]

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-2194

Description

• Here are some details about my PR, including screenshots (if applicable):

As part of #4095, a bug was introduced where the Metrics Scope object was not being closed, resulting in a non-daemon thread being alive. This resulted in AM container not getting shut down on application completion.

This PR implements the fix to close metrics scope wherever it is initialized.
It also covers calling close on JobLauncher upon its completion, which now results in cleanly closing the resources launched by JobLauncher.
Instead of calling executeCancellation() directly we now call cancelJob() in GobblinJobLauncher.close() since the latter cancels the job in synchronized manner which in turn calls executeCancellation().

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
  Tested in a local project where the application master shuts down.
  

ApplicationLauncher has already stopped gets printed when the shutdown hook gets called from ServiceBasedAppLauncher indicating a JVM shutdown.
Having the same state as the AM shutdown container fix PR. See the Tests section here.

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"

[iPalash]

This change impacts many child classes

Even though none of them implement the executeCancellation method but this is still a divergence which should be documented IMO

[abhishekmjain]

Can you elaborate on what documentation you feel should be added?
The executeCancellation is a No-Op function implemented in GobblinJobLauncher