[LSQ] Minor fixes and simplifications

[MaxWipfli]

This includes a number of small fixes and improvements to the LSQ generator that have been cherry-picked from my semester project code.

• Clean up computation of empty{Ld,St}AddrW in the configuration
• Add assertions to ensure load/store queues are large enough so that all groups can be allocated.
• Add missing pipeline register ldq_head_oh_pcomp
• Simplify the IntToBits helper function and add clear error messages (e.g., for negative inputs)

[MaxWipfli]

cc @JasmijnB regarding #914

[murphe67]

Thanks for pulling these out of the rest of your stuff Max 😁