filter: add per-aggregate filter to configure max_io_ops_per_host

Adds a filter AggregateIoOpsFilter whichprovides the ability
to read from aggregates metadata "max_io_ops_per_host".

DocImpact
Implements: blueprint per-aggregate-max-io-ops-per-host
Change-Id: I086033e7904c16995298bee7196ad3e7b5dc7aaf
Merge "filter: add per-aggregate filter to configure max_io_ops_per_host"