ci(doc): add doc build caching

[PProfizi]

The goal is to accelerate doc building using cached Sphinx build files whenever possible.

The caching logic is to retrieve, by order of priority:

• the cache from last run on this branch
• the cache from master

The cache should only contain files where Sphinx can detect changes:

• this is true for modules used by AutoAPI
• this is true for example scripts

The cache could be based on the hash of a lock file, as differences in installed graphics dependencies could result in changes despite Sphinx not detecting changes in the actual scripts.
That means however the cache will only work if no changes in dependencies.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.10%. Comparing base (3f5994b) to head (a749326).
Report is 9 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2342   +/-   ##
=======================================
  Coverage   84.09%   84.10%           
=======================================
  Files          91       91           
  Lines       10522    10529    +7     
=======================================
+ Hits         8849     8855    +6     
- Misses       1673     1674    +1     

[github-actions]

The documentation for this pull request will be available at https://dpf.docs.pyansys.com/pull/2342. Please allow some time for the documentation to be deployed.

[github-actions]

Some tests with 'continue-on-error: true' have failed:

• PyDPF-Post docstring tests on windows-latest

Created by continue-on-error-comment

[PProfizi]

@Revathyvenugopal162 pinging you FYI, this PR tries to use a few sphinx tricks to improve config change detection.
It then tries to add a caching logic to the pipelines to see how short we can the doc build step.
This is work in progress.
As you mentioned on the ansys-sphinx-theme issue, there are definitely extensions still triggering a rebuild somewhere.