Previously, the `catch_discover_tests` would prepare the entire CTest
command (e.g. `add_test(...)` or `set_tests_properties(...)`) first, and
then escape it when finished. However, this caused lot of the command args
to be escaped over and over again (e.g. executable name or Catch2's reporter
args), for no reason, as they were always the same, and thus their escaping
was always the same.

Until recently, the performance overhead didn't matter as there were many
spots which had quadratic runtime in number of tests. However, the recent
refactorings fixed these, and this commit now improves the throughput by
10-20%.

Also extended the benchmarked COUNTS in `benchmark_discovery.py`,
because the performance is now good enough that it is reasonable
to benchmark 16k tests.

* Quiet verbosity provides just the test names
* Normal verbosity adds tags
* High verbosity add the source location of the tests

Listing tests with the quiet verbosity results in about 1/4 of the
previous output, which leads to measurably faster execution of
`catch_discover_tests` when it does not need tags for labels.
(If it does need tags, the output is about 1/2 of previous).