Removes a bulk of rust crates that we no longer need, but that added significant install, build and testing time to the Rust parser.
Most significantly, removed `enso-web` and `enso-shapely`, and got rid of many no longer necessary `#![feature]`s. Moved two still used proc-macros from shapely to prelude. The last remaining usage of `web-sys` is within the logger (`console.log`), but we may actually want to keep that one.
