ci: use own DPF standalone Docker image reference in workflows

[germa89]

Description

As the title.

Issue linked

Related #3852

Checklist

• I have visited and read Develop PyMAPDL.
• I have tested my changes locally
• I have added necessary documentation or updated existing documentation.
• I have followed the PyMAPDL coding style guidelines.
• I have added appropriate unit tests that also ensure the minimal coverage criteria.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have marked this PR as draft if it is not ready to be reviewed yet.
• I have made sure that the title of my PR follows Commit naming conventions (e.g. feat: adding new MAPDL command)

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[germa89]

@pyansys-ci-bot LGTM.

[pyansys-ci-bot]

✅ Approving this PR because germa89 said so in here 😬

[germa89]

Failing at the moment. Waiting for ansys/pydpf-core#2254

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.28%. Comparing base (fb448fb) to head (2ce1b91).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3882   +/-   ##
=======================================
  Coverage   88.27%   88.28%           
=======================================
  Files         187      187           
  Lines       14830    14830           
=======================================
+ Hits        13091    13092    +1     
+ Misses       1739     1738    -1     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[germa89]

I had to change the docker image from ubuntu to rocky OS. For some reason, the ubuntu version does not work.

[germa89]

Remote: v25.1-ubuntu-student / test-remote is failing and I dont know why.

The other setups (remote v24.2 and v25.2/latest) are working fine.

[germa89]

Remote: v25.1-ubuntu-student / test-remote is failing and I dont know why.

The other setups (remote v24.2 and v25.2/latest) are working fine.

My fault, I did overwrite the DPF image with the daily built. That is why I had to specify Rocky version of the standalone docker image.