Problem: No way to check the version of a treesitter parser.
Solution: Add version metadata (ABI 15 parsers only) as well as parser state count and supertype information (ABI 15) in `vim.treesitter.language.inspect()`. Also graduate the `abi_version` field, as this is now the official upstream name.
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Co-authored-by: Christian Clason <c.clason@uni-graz.at>