Add coc.preferences.formatterExtension configuration

[statiolake]

This is a proof-of-concept.

• Registered by extensions itself (like coc-pyright): identified by extension name as expected
• Registered by extensions through a language client (like @yaegassy/coc-ruff): identified by extension name as expected
• Registered by coc.nvim for raw LSP languageserver configuration: identified as coc.nvim
  • TODO: So there is no way to select one from multiple LSP - what it should be in this case?

Priorities are still expected to work (when coc.preferences.formatterExtension is null).

Closes #5076

[codecov]

Codecov Report

Attention: Patch coverage is 65.21739% with 16 lines in your changes missing coverage. Please review.

Project coverage is 98.41%. Comparing base (c5ffbb3) to head (867603a).

Files	Patch %	Lines
src/provider/formatManager.ts	50.00%	8 Missing ⚠️
src/provider/formatRangeManager.ts	50.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5102      +/-   ##
==========================================
- Coverage   98.47%   98.41%   -0.06%     
==========================================
  Files         273      273              
  Lines       26088    26123      +35     
  Branches     5389     5396       +7     
==========================================
+ Hits        25689    25708      +19     
- Misses        239      255      +16     
  Partials      160      160              

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[fannheyward]

I've tested this and works as expected, thank you for your PR, the parseExtensionName function is a gem.

[fannheyward]

Please add the update to history.md and typings/index.d.ts too.

[statiolake]

Thank you for your checking!

For index.d.ts, is it correct understanding that it is listing public APIs of coc.nvim?
If so, it is a good option to keep the public API as-is to "hide" this extra implementation detail; an extension name is not what should be explicitly specified from an extension's side. What do you think? If you think we should include it in index.d.ts, I'll do that. And if to keep the current one, I'll add an explanation to the implementation side why this signature is different from the index.d.ts one.

Also, should I add some tests for this? The problem is that I'm not familiar with neither JavaScript's testing ecosystem nor coc.nvim's testing utilities.

[fannheyward]

OK, let's hide this from the API as the extension name won't be specified, and ignore the tests for now.

@statiolake is there any more work to add?

[statiolake]

OK, then I won't update index.d.ts and ignore tests for now. But I think I still need to add this new configuration to history.md. I'll do that later today.

[statiolake]

All done. Please check and merge this if it's OK.

[fannheyward]

doc/coc-config.txt please

[statiolake]

Sorry I didn't notice that. Now fixed.