Move max number of models enforcement to compat layer

Resource constraint enforcement is the job of the HAL starting in
V2.4, so it makes sense to push this into the compat layer.

Test: atest SoundTriggerMiddlewareImplTest SoundHw2CompatTest
      Manual verification of basic soundtrigger flows.
Bug: 178722883
Change-Id: Ic3e27a98b7f306c5a30af1e23c7d70944c514816