stack::rfcomm: Combine 2 APIs creating PORT_SetEventMaskAndCallback

Combine:

PORT_SetEventMask(...)
PORT_SetEventCallback(...)
The callback is called if an event in the corresponding bitmask is set indicating they should be logically aggregated.

Bug: 345258558
Test: m .
Flag: EXEMPT, Mechanical Refactor

Change-Id: Id5478343fd3f32ee88073b73dcacc9f775fcfff7