this commit is a little too large to document fully, however the main gist of it this
- finish the `genInlineMemcpy` implement
- rename `setValue` to `genCopy` as I agree with jacob that it's a better name
- add in `genVarDbgInfo` for a better gdb experience
- follow the x86_64's method for genCall, as the procedure is very similar for us
- add `airSliceLen` as it's trivial
- change up the `airAddWithOverflow implementation a bit
- make sure to not spill of the elem_ty is 0 size
- correctly follow the RISC-V calling convention and spill the used calle saved registers in the prologue
and restore them in the epilogue
- add `address`, `deref`, and `offset` helper functions for MCValue. I must say I love these,
they make the code very readable and super verbose :)
- fix a `register_manager.zig` issue where when using the last register in the set, the value would overflow at comptime.
was happening because we were adding to `max_id` before subtracting from it.
350ad90cee