feat: program-wide per-bb instrumentation hooks

[ndrewh]

Dynamorio instrumentation hooks typically run for every bb. Our hooks (#5) currently do not -- you have to specify the PC to insert your instrumentation at.

It might be interesting to explore whether the overhead of calling into Python for every bb is low enough for this to be practical.

[ndrewh]

We could provide a different primitive: for example, we could allow someone to specify a specific opcode they are interested in (e.g. CMP) and hook all instances of that instruction type. But then you still have to worry about having a robust instruction representation in Python (i.e. they're going to want to get the operands of the instruction, etc.) -- which we currently don't have