crypto: add tracing & warning about GNUTLS countermeasures

crypto: add tracing & warning about GNUTLS countermeasures

We want some visibility on stderr when the GNUTLS thread
safety countermeasures are activated, to encourage people
to get the real fix deployed (once it exists). Some trace
points will also help if we see any further wierd crash
scenario we've not anticipated.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/qemu-devel/20250718150514.2635338-5-berrange@redhat.com
[add missing include]
Signed-off-by: Fabiano Rosas <farosas@suse.de>