Add compatibility mode for Vertico

[axelf4]

This pull request adds a compatibility mode for the Vertico completion system that sets it up to lazily apply highlighting to Hotfuzz completions.

This is motivated by a desire to reach feature parity between Vertico and Selectrum, due to the potentiality of Selectrum being sunset, see minad/vertico#237.

Do you have any thoughts on this @minad? Advicing foreign functions in library code is something I would rather avoid, but here I think the utility outweighs the trouble of possible breakages caused by any future Vertico updates.

Also relevant to #2.

[codecov]

Codecov Report

Merging #3 (ac49577) into master (7f8f351) will decrease coverage by 14.88%.
The diff coverage is 0.00%.

❗ Current head ac49577 differs from pull request most recent head 8b1676d. Consider uploading reports for the commit 8b1676d to get more accurate results

@@             Coverage Diff             @@
##           master       #3       +/-   ##
===========================================
- Coverage   90.32%   75.43%   -14.89%     
===========================================
  Files           1        1               
  Lines          93      114       +21     
===========================================
+ Hits           84       86        +2     
- Misses          9       28       +19     

Impacted Files	Coverage Δ
hotfuzz.el	75.43% <0.00%> (-14.89%)	⬇️

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[minad]

The advice is okay, since I use the same in Vertico. See https://github.com/minad/vertico/blob/e5935b5bbfc0d820c54ed1ad52e36e8c48248fd7/vertico.el#L266-L302. In the future we may upstream the filtering/highlighting separation to Emacs itself, but the last time I tried the efforts have stalled. Technically the completion styles already perform filtering and highlighting separately, it is just not exposed by the completion-all-completions API. vertico--all-completions kind of fixes this.