Use annotations to identify stopping points in the start/stop API

Today the start/stop API assumes the call to the stop point will be easily recognized as a control transfer to a separate PC for the callee. This breaks down for statically-linked DR with inlining (#3549) and also had trouble with static DR with bounds identification (#3387, though the incorrect DR bounds there likely caused other problems as well).

This issue proposes having the stop routines insert annotations and relying on DR's annotation identification to figure out when a stop routine is reached. This should be more robust and reliable than the current solution.