ci: make pydpf-post job information-only

[PProfizi]

The PyDPF-Core CI runs PyDPF-Post tests for information purposes thanks to its pydpf-post.yml workflow.
This PR makes sure that the workflow is always reported as successful to not stop people from merging, while still reporting errors for PyDPF-Post tests as comments in the PR if any.
This is most useful for server-sync PRs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.77%. Comparing base (f55da78) to head (a2d1f30).
Report is 2 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2272      +/-   ##
==========================================
- Coverage   83.84%   83.77%   -0.08%     
==========================================
  Files          90       90              
  Lines       10396    10396              
==========================================
- Hits         8717     8709       -8     
- Misses       1679     1687       +8     

[PProfizi]

Here is a CI run on the daily standalone (where pydpf-post tests fail), still reporting PyDPF-Post workflow as passing https://github.com/ansys/pydpf-core/actions/runs/14966392212

[PProfizi]

@rafacanton the continue-on-error already makes the workflow go green despite PyDPF-Post tests failing as you can see in the CI in the previous comment.
I just added use of a continue-on-error-comment action, which we can test by merging this and then updating the daily server-sync PR currently failing, to see if comments do appear.
In any case it will have solved the initial issue.