Make `LanguageFeatureRequestDelays` easier to use and adopt in more places

[jrieken]

We have adaptive debouncing logic implemented in LanguageFeatureRequestDelays. We should make this so that it can be used in more places easier. Identified the following pieces

• a better sliding window average instead of "forever move average"
• in all providers, to save on bandwidth, if a request is canceled, throw canceled instead of returning results
• adopt ILanguageFeatureDebounceService#for in more providers e.g.
  • semantic tokens,
  • folding
  • colors @aeschli
  • linked editing @aeschli
  • document links @alexdima
  • debug inline values @weinand
  • inline completions @hediet