feat(diagnostics): implement endpoint for JMX threadinfo dump

[andrewazores]

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Based on #644
Related to #135

Description of the change:

This change allows an environment variable to be configured so that...

Motivation for the change:

This change is helpful because users may want to...

How to manually test:

1. Run CRYOSTAT_IMAGE=quay.io... bash smoketest.bash...
2. ...

[github-actions]

This PR/issue depends on:

• feat(diagnostic): implement diagnostics class with gc invocation operation #644
  By Dependent Issues (🤖). Happy coding!