Implements:
- UUIDs: https://www.pivotaltracker.com/story/show/182931137
- Comments: https://www.pivotaltracker.com/story/show/182981779
- Type annotations and signatures: https://www.pivotaltracker.com/story/show/182497454
- Fix getter names (https://github.com/enso-org/enso/pull/3627#discussion_r940887460).
# Important Notes
- I can't fully test UUIDs; I have tested that the data obtained in Rust matches my understanding of how the format is supposed to work. What remains to be tested is that the data in Java matches the way the old parser handles the format. So @JaroslavTulach, let me know if you see any cases where I'm not returning the same values.
- This implementation of type annotations and signatures accepts any expression in type context. It would probably be nice to narrow this down at some point, but for now I have no design info on what specifically should be allowed in type expressions; this implementation should be at least an incremental improvement.
Provide a JNI dynamic-library interface to `enso_parser`.
# Important Notes
- The library can be built with: `cargo build -p enso-parser-jni`.
- A new `org.enso.syntax2.Parser` API is implemented on top of the JNI interface provided by `enso-parser-jni`.
- We are using the `jni` crate, since apparently Java cannot just call C-ABI functions. The crate is not well-maintained. I came across an obviously-unsound `safe` function, and found it was reported over a year ago, with a PR to fix: jni-rs/jni-rs#303. However our needs are simple. We can't trust any safety guarantees they imply, but I think we are unlikely to encounter any logic bugs using the basic bindings.
