Speed up tree-sitter-language update script

[Luni-4]

• Consider only the files associated to a tree-sitter-language when rust-code-analyses computes the metrics
• Compare metrics in parallel using the multiprocess package

[marco-c]

Using async would be nicer than multiprocessing and give you a similar level of parallelism (most of the time is likely spent in executing programs and reading files, so what you want to parallelize is waits rather than computation, and async achieves that). multiprocessing in Python is pretty painful.

[Luni-4]

Using async would be nicer than multiprocessing and give you a similar level of parallelism (most of the time is likely spent in executing programs and reading files, so what you want to parallelize is waits rather than computation, and async achieves that). multiprocessing in Python is pretty painful.

True, I haven't thought about async, thank you! :)