Completion (and renaming) behaves incorrectly on labels with colons about texlab

[pfoerster]

@thomasfaingnaert suggests not using labels for completions but rather text-edits, which is a newer part of the LSP protocol.

The server now uses the textEdit field in CompletionItem.
In your example, the completion now works correctly.

(A related issue is with renaming: if I rename sec:foo_bar, the prefilled text is just foo_bar, but the whole label (including sec:) is replaced with what I write. This is much less critical, of course.)

The server now implements the textEdit/prepareRename request so this issue should be fixed as well.

[clason]

Great, thanks!