[profiler] Split method_leave callback into a method_tail_call callback.

[profiler] Split method_leave callback into a method_tail_call callback.

With this, profilers can distinguish between the two, and also know what the
target method of a tail call is.

The call instrumentation flags have been renamed accordingly and a new flag has
been added for instrumenting tail calls. I've also added a flag for exceptional
leave events, and method_exception_leave is only raised if this flag is given
for a method.

Also refactored the relevant JIT code a bit so it's easier to follow.