Sample instrumentation for basic block code coverage

On the entry of every basic block, inject a call to a tracing method:

   CodeCoverage.TraceBasicBlock(block_id)

This is a slightly more complex instrumentation compared to inserting
entry/exit hooks since it requires allocating scratch registers and the CFG.
As such, is both a sample of how code coverage can be implemented and an
very aggressive stress test for bytecode modification.

Test: bazel test :dexter_tests

Change-Id: If496292f15bfcf6a396751e68a77d31f131fb32b