Deprecate get/update/deleteModel and STDetector

These APIs are malformed/bug-prone and can lead to unclear model state.
They also introduce unnecessary disk-reads in certain call flows.
There is also no compelling reason to offer persisting model state as
an affordance of STService.

STDetector doesn't guarantee callback delivery. Registering a service
with STManager should be preferred. It also has an unclear lifecycle
model.

Test: None
Bug: 266963008
Change-Id: I0acf614518f441788b469846bfcc1fd8ae6a7342