Follow-up to #28490
Problem:
The new behaviour of goto_next/prev() of navigating to the next highest
severity doesn't work well when diagnostic providers have different
interpretations of severities. E.g. the user may be blocked from
navigating to a useful LSP warning, due to some linter error.
Solution:
The behaviour of next highest severity is now a hidden option
`_highest = true`. We can revisit how to integrate this behaviour
during the 0.11 cycle.
ee41153a94