ci(linux-asan/linux-ubsan): let's save some time

ci(linux-asan/linux-ubsan): let's save some time

Every once in a while, the `git-p4` tests flake for reasons outside of
our control. It typically fails with "Connection refused" e.g. here:
https://github.com/git/git/actions/runs/5969707156/job/16196057724

	[...]
	+ git p4 clone --dest=/home/runner/work/git/git/t/trash directory.t9807-git-p4-submit/git //depot
	  Initialized empty Git repository in /home/runner/work/git/git/t/trash directory.t9807-git-p4-submit/git/.git/
	  Perforce client error:
		Connect to server failed; check $P4PORT.
		TCP connect to localhost:9807 failed.
		connect: 127.0.0.1:9807: Connection refused
	  failure accessing depot: could not run p4
	  Importing from //depot into /home/runner/work/git/git/t/trash directory.t9807-git-p4-submit/git
	 [...]

This happens in other jobs, too, but in the `linux-asan`/`linux-ubsan`
jobs it hurts the most because those jobs often take an _awfully_ long
time to run, therefore re-running a failed `linux-asan`/`linux-ubsan`
jobs is _very_ costly.

The purpose of the `linux-asan`/`linux-ubsan` jobs is to exercise the C
code of Git, anyway, and any part of Git's source code that the `git-p4`
tests run and that would benefit from the attention of ASAN/UBSAN are
run better in other tests anyway, as debugging C code run via Python
scripts can get a bit hairy.

In fact, it is not even just `git-p4` that is the problem (even if it
flakes often enough to be problematic in the CI builds), but really the
part about Python scripts. So let's just skip any Python parts of the
tests from being run in that job.

For good measure, also skip the Subversion tests because debugging C
code run via Perl scripts is as much fun as debugging C code run via
Python scripts. And it will reduce the time this very expensive job
takes, which is a big benefit.

Backported to `maint-2.39` as another step to get that branch's CI
builds back to a healthy state.

Backported-from: 6ba913629f (ci(linux-asan-ubsan): let's save some time, 2023-08-29)
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>