Add AggregateRamFilter

Implements blueprint per-aggregate-resource-ratio

* AggregateRamFilter to support per-aggregate ram_allocation_ratio
* Falls back to global setting if per-aggregate value not found

DocImpact

Change-Id: I93e069f0ac3f595d9a2a17119274c7bfbe8fca31
Merge "Add AggregateRamFilter"