Ability for skip to report a message saying why a test is skipped

[nickrobinson251]

we have code that uses tags on testitems with a filter function passed to runtests in order to skip tests e.g.

@testitem "foo" tags=[:recmod_incompat] begin
   # tests here
end

function check_recovery_mode(test_item)
    should_run = true
    if RECOVERY_MODE()
        should_run = !(:recmode_incompat in test_item.tags)
    end
    if !should_run
        @warn "Skipping test `$(test_item.name)` because it is \
        incompatible with recovery mode."
    end
    return should_run
end
runtests(check_recovery_mode, ...)

This is preferred because it allows printing a message about why a testitem is being skipped, which is important when there are multiple conditions e.g.

@testitem "foo" tags=[:recmod_incompat, gapmode_incompat] begin
   # tests here
end

here we'd log the testitem is skipped because of recmode_incompat, whereas if we'd used skip like

@testitem "foo" skip=:(RECOVERY_MODE() || GAP_MODE()) begin
   # tests here
end

we would not know which condition were true.

[nickrobinson251]

a suggestion from @charnik:

We could drop the extra function in runtests() if we can setup ReTestItems such that it knows which tags to skip and the reason why. Like passing a dictionary skip_tags = Dict(:recmode_incompat => "Skip reason") or setting an environment variable RETESTITEMS_SKIPTAGS="recmode_incompat:\"Skip reason\"; gapmode_incompat:\"Another skip reason\""