Log information on specific compression backends in the OOM handler.

This patch adds some additional logging to circuits_handle_oom() to give
us more information about which specific compression backend that is
using a certain amount of memory.

See: https://bugs.torproject.org/25372
1 job for bugs/25372 in 7 minutes and 45 seconds (queued for 15 seconds)
Status Job ID Name Coverage
passed #54811333