Move IMS metrics collection callback to a static map in ImsManager

Remove the old dependency on ImsConfigListener in ImsManager and
move to a static map that is shared for all instances of ImsManager
for metrics collection.

Fixes: 173715434
Fixes: 173826270
Test: atest ImsCommonTests
Change-Id: I830833275df111b132cf58bf1586a7618de96eff