Validate that we don't have more than three captures on a single tree node

[AndreasArvidsson]

Tree sitter has a limitation of three captures per node. If you supply more than three the latter ones will just silently be dropped. We should validate this ourself and throw a proper error.

https://github.com/cursorless-dev/cursorless/blob/181cd9f5c2a47c460de01a7102bf89ee9d964d5a/packages/cursorless-engine/src/languages/TreeSitterQuery/validateQueryCaptures.ts