completion: selectively use debugpathcomplete in bash_completion
The current bash_completion code can be very slow in a large working
directory. It always uses "hg status" to generate possibly matching
files, which checks the status of every file. We often don't care
about status when completing, so that cost is very high.
As the new debugpathcomplete command does not check the status of
files, it offers much better performance for commands that only
care about completing names.
Testing that hghave does not crash when checking features
$ "$TESTDIR/hghave" --test-features 2>/dev/null