Fix potential github action smells

[ceddy4395]

Fixes

Hey! 🙂 I want to contribute the following changes to your workflow:

• Avoid running CI related actions when no source code has changed
• Avoid executing scheduled workflows on forks
• Avoid jobs without timeouts

(These changes are part of a research Study at TU Delft looking at GitHub Action Smells. Find out more)

Proposed Changes/Todos

Pull Request checklist:

• [ ] I've named my PR in the form of "Fixes #issue. Terse description."
• [ ] My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• [ ] My code follows the Terminal.Gui library design guidelines
• [ ] I ran dotnet test before commit
• [ ] I have made corresponding changes to the API documentation (using /// style comments)
• [ ] My changes generate no new warnings
• [ ] I have checked my code and corrected any poor grammar or misspellings
• [ ] I conducted basic QA to assure all features are working

[dodexahedron]

Also, a thought for future consideration for us before it disappears from my head again:

Especially with regards to Roslyn analyzers/generators, we may want to consider caching, so that they don't have to get built every time, unless one of the analyzer projects is actually modified. Would speed up the build actions. Efficiency of those actions does matter, because there is a limit to how much execution time is allowed per month.

[tig]

Is this ready for me to merge?