Fix #6643 Respect --no-run-tests, --no-run-benchmarks when listing actions

[mpilgrem]

See:

• Respect --no-run-tests, --no-run-benchmarks when listing actions #6643

Puts notification (if enabled) in Stack.Build.Execute.executePlan'.

In Stack.Build.Execute.toActions:

• does not add action singleTest if not runTests; and
• does not add action singleBench if not runBenchmarks.

Please include the following checklist in your pull request:

• Any changes that could be relevant to users have been recorded in ChangeLog.md.
• The documentation has been updated, if necessary

Please also shortly describe how you tested your change. Bonus points for added tests!

[mpilgrem]

@theobat, as you have been looking at the architecture of Stack, I would be very grateful if you could spare any time to look at this pull request, as I consider its change to be architectural (even if it is relatively minor).

[theobat]

@mpilgrem It looks good to me, though I'd place a user visible warning in case the unreachable code is reached, with an invitation to open an issue.
Also I'm wondering if stack should not prevent tests from being built in case they are disabled, I don't know, the good build behavior is not obvious to me...