qtest: introduce qtest_init_ext

qtest: introduce qtest_init_ext

Merge qtest_init_with_env_and_capabilities() and qtest_init_with_env()
into one qtest_init_ext().

Reasons:

1. qtest_init_with_env() is just wrong: it gets do_connect parameter
   but always pass true to qtest_init_with_env_and_capabilities().
   Happily, all qtest_init_with_env() callers pass true as well.

2. qtest_init_with_env() is not used outside of libqtest.c, so no
   reason to keep it as public function

3. and in libqtest.c it's used not often, so no problem to use
   more generic function instead.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <20250410162250.329941-1-vsementsov@yandex-team.ru>
Signed-off-by: Fabiano Rosas <farosas@suse.de>