Floss: Add log panics in btmanagerd

This makes rust panics able to print some message before it crashes.

Bug: 316228791
Test: modify code to intentionally panics in btmanagerd. verify that
the panics message is printed in /var/log/btmanagerd.
Test: mma -j
Tag: #floss

Change-Id: Iafcaf344f6dfa09558c5367e3b076772e5e4447b