Make unverified register allocator print function names

This should involve modify unverified/reg_alloc/reg_alloc.sml (and files that use it) to print the relevant names instead of the function index.

Suggested by @myreen

Start by reading unverified/reg_alloc/reg_alloc.sml and then inspect the files that use it, as indicated in the issue. Trace where the register allocator currently prints a function index and identify the available function-name information. The work is done when the relevant names are printed instead of function indices throughout the affected paths.

Written by the indexing model from the issue text.