Investigate using stabby for ABI details

[silvanshade]

See https://github.com/ZettaScaleLabs/stabby

[silvanshade]

Preliminary ideas for how this could be useful:

• use for translating more types across FFI
  • how do we use stabby on the C++ side?
• use for verifying optimal layout: see https://docs.rs/stabby/latest/stabby/#structures
  • probably limited utility unless (or until) we start exposing internal struct fields (needs ClangImporter)
• use for including canaries: see https://docs.rs/stabby/latest/stabby/#stabbyexportcanaries
  • catch potential ABI incompatibilities between clang and gcc
  • can we detect at final build-time (second phase, after abi inference and codegen) a mismatch?
  • under which scenarios would a mismatch even be possible?
    • accidental overrides of CXX, cargo environment, or build.rs compiler selection?