This PR re-enables semantic tokens for Verso docstrings, after a prior
change accidentally disabled them. It also adds a test to prevent this
from happening again.
In the process, it became clear that there was a bug. The highlighting
strategy led to overlapping but not identical tokens, but the code had
previously assumed that this couldn't happen at the delta-encoding step.
So this PR additionally replaces the removal of duplicate tokens with
priority-based handling of overlapping tokens.
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Co-authored-by: Marc Huisinga <mhuisi@protonmail.com>
