* Show argument completions even if it has more than 255 chars
* use tokenBefore for existingKeys
* use 'ShortArg' token so braces are escaped
* refactor argument completion logic
* remove extra filter
* Add makeMultipleArgumentCompletionSource for arguments with multiple keys
* revert makeArgumentCompletionSource
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Co-authored-by: Alf Eaton <alf.eaton@overleaf.com>
GitOrigin-RevId: f5aa70fe5e58e04efe0c4e8668957f61a7fa7911