CLEANUP: mux-quic: remove usage of non-standard ull type

CLEANUP: mux-quic: remove usage of non-standard ull type

ull is a typedef to unsigned long long. It is only defined in
xprt_quic-t.h. Its usage should be limited over time to reduce xprt_quic
dependency over the whole code. It can be replaced by ullong typedef
from compat.h.

For the moment, ull references have been replaced in qmux_trace module.
They were only used for printf format and has been replaced by the true
variable type.

This change is useful to reduce dependencies on xprt_quic in other
files.

This should be backported up to 2.6.