test_sorcery_memory_cache_thrash: Add unit tests for thrashing the memory cache.

This change adds a CLI command which can perform memory cache thrashing as well
as unit tests which perform thrashing under the following configurations:

1. Low number of unique objects that go stale after 1 second
2. Low number of unique objects that expire after 1 second
3. Low number of unique objects which are constantly updated
4. Large number of unique objects which exceed a defined cache size
5. Large number of unique objects which exceed a defined cache size
   that also expire and go stale rapidly
6. Large number of unique objects which expire and go stale rapidly
7. Large number of unique objects

For all of the above there are a large number of threads constantly
attempting to retrieve random objects and each test runs for a few
seconds.

ASTERISK-25067
Reported by: Matt Jordan

Change-Id: I8c8ceff977332c80ed4a31f10d694d48552b2f78