Add diagnostics to help users know when to insert typealias:

[virtuald]

The result is that lines like the following get inserted into the various autogenerated files:

  // semiwrap diagnostic: if this line fails because `XXX` is unknown,
  // add a typealias entry for `XXX` to /absolute/path/to/Whatever.yml.
  using semiwrap_typealias_probe_XXX__add_typealias_to_yaml [[maybe_unused]] = XXX;

If XXX fails to resolve then the compiler error is hopefully a little more helpful, but maybe at the expense of additional symbols in the binary (maybe we can tell the compiler to not export it?)

However, if we were smarter about using namespaces in semiwrap, perhaps some of this wouldn't be needed.

Currently this is 100% slop and I haven't manually reviewed it yet. However, it can build mostrobotpy in its current state, so that implies it's not totally broken?