Improve ocaml-tree-sitter error messages so that they make sense in wider context

[mjambon]

@joseemds wrote:

Also improving error messages is important, while trying it i had no idea what Error: Aliases are not suported meaned, maybe turn it more explicative like Error: Aliases are not suported, use simplify-grammar and try again with the new generated file, although adding gen-c to the workflow would make this not necessary, would still be useful.

The idea is to check all the error messages currently produced by ocaml-tree-sitter, take a step back and add suggestions about what to do in the context of the full pipeline.