Figure out if there is a good way to get location debug info into selene panic errors

[tatiana-s]

[jake-arkinstall]

I don't know what the lowering implementation will look like, but in my mind a lot of this has to happen there:

• I believe resolving debug information (file, line, or a stack of those) needs to happen within the lowered LLVM itself
  • I don't think we can do this by traversing the stack from within libselene
• We can add a custom debug_panic call that accepts this information in an agreed-upon format and emits it to the result stream
• We can flush it multi-part into the result stream and handle it when reading, so I'm not too concerned about string size limitations within realistic scenarios.