[dv] Psuedo instruction coverage for Bitmanip

[GregAC]

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 #1228