qtest/qom-test: Shallow testing of qom-list / qom-get

qtest/qom-test: Shallow testing of qom-list / qom-get

This test traverses the QOM sub-tree rooted at /machine with a
combination of qom-list and qom-get.  In my x86_64 testing, it runs
almost 12000 QMP commands in 34 seconds.  With -m slow, we test more
machines, and it takes almost 84000 commands in almost four minutes.

Since commit 3dd93992ffb (tests/qtest/qom-test: unit test for
qom-list-get), the test traverses this tree a second time, with
qom-list-get.  In my x86_64 testing, this takes some 200 QMP commands
and around two seconds, and some 1100 in just under 12s with -m slow.

Traversing the entire tree is useful, because it exercise the QOM
property getters.  Traversing it twice not so much.

Make the qom-list / qom-get test shallow unless -m slow is given:
don't recurse.  Cuts the number of commands to around 600, and run
time to under 5s for me.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20250725135034.2280477-3-armbru@redhat.com>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>