fix(gha): run meta jobs on maintenance branches

[gforcada]

Closes #337

As it was restricted to main and master any maintenance branch, say 3.x would never run GHA from this file, i.e. qa, dependencies, coverage, etc.

[mauritsvanrees]

Testing this in plone/plone.namedfile#203

I was mostly checking if any jobs would run double: once for being a push and once for being part of a pull request. But that does not happen. That is good.

But: if there is a PR with a branch from outside the plone org, I'm not sure if any tests are run. Well, it is still a push to a branch, so probably fine. But we may want to test.

Oh, I would definitely want to keep the workflow_dispatch option.

[mauritsvanrees]

I was mostly checking if any jobs would run double: once for being a push and once for being part of a pull request. But that does not happen. That is good.

But: if there is a PR with a branch from outside the plone org, I'm not sure if any tests are run. Well, it is still a push to a branch, so probably fine. But we may want to test.

I created a branch from a fork:
plone/plone.namedfile#204
The 'on push' tests are executed, so that is fine.

Then I included pull_request there as well, and as expected this doubled the amount of jobs. So leaving out pull_request is fine.

Theoretically it could be nice to use on push for main, master and *.x (if that is supported) and on pull_request without restrictions. Then a push to my-WIP-branch would not run any jobs, until I am ready and create an actual PR from that branch. But that is a bit tricky and without much value.

[mauritsvanrees]

I have pushed a commit to restore the workflow_dispatch trigger in meta.yml

I have added this workflow_dispatch trigger for generated test-matrix workflows as well. I am surprised it was not there yet.