[sanitizer_common] Recycle StackDepot memory

This relates to https://reviews.llvm.org/D95835.

In DFSan origin tracking we use StackDepot to record
stack traces and origin traces (like MSan origin tracking).

For at least two reasons, we wanted to control StackDepot's memory cost
1) We may use DFSan origin tracking to monitor programs that run for
   many days. This may eventually use too much memory for StackDepot.
2) DFSan supports flush shadow memory to reduce overhead. After flush,
   all existing IDs in StackDepot are not valid because no one will
   refer to them.