CI/GHA: Add stale activity action for issues and PRs

[thrasher-]

PR Description

Adds a GHA for stale issues/PRs. By default, the following settings have been defined however these are set via GH envs which make it easy to adjust these without having to commit changes. The settings will also be displayed each time the job is run however they're listed below:

Runs every Monday-Friday during AEST/AEDT hours at midnight UTC which is 10AM-11AM AEST/AEDT.
Days before an issue or PR goes stale: 30 days.
Days before an issue is closed after going stale: 7 days.
PRs will never be closed automatically.
Will automatically set the tag of the PRs/issues to stale.

Tag exemptions:
Issues: in progress,todo
PRs: nomerge requires dependency,blocked

Type of change

• New feature (non-breaking change which adds functionality)

How has this been tested

• Own fork

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation and regenerated documentation via the documentation tool
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally and on Github Actions with my changes
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.94%. Comparing base (ba77c99) to head (d0a043a).
Report is 60 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1689      +/-   ##
==========================================
+ Coverage   36.92%   36.94%   +0.01%     
==========================================
  Files         414      414              
  Lines      180509   180512       +3     
==========================================
+ Hits        66660    66688      +28     
+ Misses     106025   105997      -28     
- Partials     7824     7827       +3     

see 16 files with indirect coverage changes

[gloriousCode]

Had a peruse of https://github.com/actions/stale/blob/main/action.yml
Looks like you've set it up to do everything I'd want from it

ACK!

[shazbert]

LGTM!