[JENKINS-72112] Allow merge strategy inheritance in PodTemplates

[vivienfricadelamadeus]

https://issues.jenkins.io/browse/JENKINS-72112

Testing done

### Submitter checklist
- [ ] Make sure you are opening from a **topic/feature/bugfix branch** (right side) and not your main branch!
- [ ] Ensure that the pull request title represents the desired changelog entry
- [ ] Please describe what you did
- [ ] Link to relevant issues in GitHub or Jira
- [ ] Link to relevant pull requests, esp. upstream and downstream changes
- [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[igor-nikiforov]

We are faced with this issue too.

@vivienfricadelamadeus are you planning to continue work on this PR? Thanks.

[vivienfricadelamadeus]

@igor-nikiforov Actually we found a workaround on our side (not directly linked to this feature), so I left the PR as it is for now. Don't hesitate to fork it

[Vlatombe]

Superceded by #1513