This is a quick fix for #25296 actually reverting the commit
a708c988, replacing the Hold/Release
lifecycle used there by an ad-hoc Hold/Release which actually defer the
actual release by blocking instead of releasing in the preparser thread.

Indeed, libvlc_media is holding the instance used to create it, though
it only needs it for preparsing. If the last reference of the media is
hold by the preparser, libvlc_media will be released by the preparser
thread and the libvlc_instance potentially released from there too.
Since killing the libvlc_instance will join the preparser thread, it
cannot be done from the preparser thread, or would lead to the failure
detailed in #25296. Written differently, only the final client should
make use of Hold/Release, directly through the adequate function or
indirectly through the creation of new objects.

In addition, a708c988 cannot just be
reverted as it was fixi...