ZJIT: Add fast path for String#byteslice with 2 args

[tekknolagi]

Call rb_str_byte_substr

[tekknolagi]

This will help protoboeuf

[tekknolagi]

This probably involves making a StringByteslice opcode and annotating in src/cruby_methods.rs

[dak2]

I was curious about how this works internally, so I looked into it and ended up with a draft PR: ruby#18568

As I understand it, only the two-argument form is specialized and everything else falls back to the existing call path.
Corrections and advice are very welcome :)

I haven't run any benchmarks yet, but I'd like to keep working on this.
Let me know if this cuts across work you already have planned.