Refactor deoptimization support in debugger

This CL prepares breakpoint support for inlined methods where we'll have to
deoptimize everything.

We move deoptimization-related information to Dbg class only (deoptimization
request queue, full deoptimization event count and deoptimization lock). We
replace MethodInstrumentionRequest by DeoptimizationRequest. This is used to
know which kind of deoptimization is required for a particular event.

It also simplifies lock ordering a bit during event setup: we no longer need to
hold the deoptimization lock while holding the breakpoint lock. Moreover, the
deoptimization lock should be held only after the event list lock.

Bug: 12187616
Change-Id: Iff13f004adaeb25e5d609238bacce0b9720510e6