Split tst_qmlformat

tst_qmlformat is slow and is doing out of process formatting for most files. Also, people have a tendency to use it to add new out of process tests that actually should be in process.
Make the distinction clear by splitting the test in two files, such that non-cli tests that don't need to spawn a qmlformat executable are implemented in tst_qmlformat that only has tools to run in-process formatting.