5526: Handle semantic token deltas r=kjeremy a=kjeremy
This basically takes the naive approach where we always compute the tokens but save space sending over the wire which apparently solves some GC problems with vscode.
This is waiting for https://github.com/gluon-lang/lsp-types/pull/174 to be merged. I am also unsure of the best way to stash the tokens into `DocumentData` in a safe manner.
Co-authored-by: kjeremy <kjeremy@gmail.com>
Co-authored-by: Jeremy Kolb <kjeremy@gmail.com>
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