res_sorcery_memory_cache: Add basic module implementation.

This change adds a basic res_sorcery_memory_cache module which implements
configuration option parsing, configuration file parsing for threading,
sorcery interface implementation, and unit tests.

Objects can be added, updated, deleted, and retrieved from the memory
cache. Automatic expiration and stale handling will be added in the
future.

Note that unit tests exist within the module itself in case the
threading done as a result of expiration results in asynchronous
actions (which it likely will). Providing access and a notification
mechanism for an external test module would be complicated and
not worth it.

ASTERISK-25067 #close
Reported by: Matt Jordan

Change-Id: Id8a6a357ef5a83d466f81eee56a67d13eeb118b9