[Profiler] Limit decl walking behavior
Unify the mapped behavior with the unmapped
behavior and only ever walk into a pattern binding
decls, top-level code decls, and non-nested
functions. This avoids walking into e.g nested
types, leading to duplicate coverage.
We don't need to handle the unmapped behavior
separately, as top-level code decls are always
explicit, and non-nested functions are always
checked when we create the profiler.
rdar://99963912
