This will solve a far amount of syntax incompatibilities such as #3038, and provide us with a parser we can very easily re-import.
And it means new syntax would always be supported in YARP early, which will be very helpful when updating to a new Ruby version.

Currently we are using a fork of the parser in JRuby, but this is very difficult to update (notably due to using different types in the fork), so migrating to YARP will address this maintenance problem.

It should also help by replacing the Ripper C extension which is slow and unreliable with the YARP Ripper backend: #2767