[dv] Psuedo instruction coverage for Bitmanip

Three bitmanip instructions seem to be missing coverage, orc.b, zext.h and rev8. They are being executed but they can be interpreted as pseudo-instruction forms of more general instructions or instructions in their own right depending on what bitmanip implementation you are using.

We should consider reworking our coverage collection to ensure executing these samples both the pseudo instruction form and the general instruction form (so it works with configs that don't have the general instruction form).

In the case of zext.h we don't implement the more general pack it uses but have to emit it in that form from the Ibex tracer due to LLVM/GCC tooling issues, see https://github.com/lowRISC/ibex/issues/1228

Start by locating the coverage collection code and the samples for orc.b, zext.h, and rev8. Determine how each sample is currently executed and how configurations without the general instruction form are handled; done means coverage exercises both the pseudo-instruction and general-instruction forms where applicable, including the zext.h/pack case.