Add lsp stub services

[ssmifi]

Closes #28

Mostly ports from langium with go-idiomatic mechanisms for customization.

I refactored the original proposal. With the exceptions of Declaration, Implementation and Type Defintion, which provide meaningful defaults, all lsp stubs only provide the plain interface.
Semantic tokens is another exception, which I kept for comparison, but I guess it will be overwritten by the more sophisticated version in #136.

Added examples for Call Hierarchy, Code lens, Semantic tokens (which will be replaced), and Inlay Hints to the statemachine example to show adopters a working example.

#	Feature	Pattern	Notes
1	Declaration	Interface-only	Default removed - duplicated Definition without adding value
2	Implementation	Interface-only	Default + ImplementationFilter removed - the "type implements" heuristic requires language-specific type-system knowledge no generic filter can provide
3	Type Definition	Interface-only	Default removed - its cross-reference heuristic never actually filtered by field
4	Semantic Tokens	—	Removed from this PR entirely; deferred to #136
5	Inlay Hint	Interface-only	Unchanged. Open question: should it get ResolvingInlayHintProvider too?
6	Signature Help	Interface-only, + separate trigger service	Split into SignatureHelpProvider and SignatureHelpTriggers
7	Call Hierarchy	Interface-only	Fixed NodeAtCursor - now uses NameFinder. Fixed in both the godoc example and the statemachine example
8	Type Hierarchy	Interface-only	Same NodeAtCursor
9	Code Actions	Interface-only, + optional resolve extension	Added ResolvingCodeActionProvider for codeAction/resolve support
10	Code Lens	Interface-only, + optional resolve extension	Added ResolvingCodeLensProvider for codeLens/resolve support.
11	Document Links	Interface-only	Unchanged. Open question: should it get ResolvingDocumentLinkProvider too?
12	Commands	Interface-only	Unchanged

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.50.

Benchmark suite	Current: 68da275	Previous: d803417	Ratio
BenchmarkWorkspaceCycle (typefox.dev/fastbelt/examples/statemachine) - MB/s	12.98 MB/s	5.21 MB/s	2.49

This comment was automatically generated by workflow using github-action-benchmark.

[msujew]

Thanks, that's very useful!

[ssmifi]

Thanks for the review @msujew. Included all suggestions.
Still under consideration:

• Should we also add the resolve support pattern to the InlayHintProvider and DocumentLinkProvider?
• Whether to keep the real-but-test-only fixture providers (grammarInlayHintProvider, grammarCodeLensProvider, grammarSignatureHelpProvider, grammarTypeDefinitionProvider) as documentation, or trim them?

[msujew]

Should we also add the resolve support pattern to the InlayHintProvider and DocumentLinkProvider?

Good idea 👍

Whether to keep the real-but-test-only fixture providers (grammarInlayHintProvider, grammarCodeLensProvider, grammarSignatureHelpProvider, grammarTypeDefinitionProvider) as documentation, or trim them?

I think we can remove them. It doesn't feel like they actually do anything beyond asserting that the interface works as intended - which isn't doing a lot to be honest.

[ssmifi]

Ok, implemented. Please have another look.

[msujew]

FYI this needs a rebase due to LSP 3.18 update conflicts. I'll have another look once this is done.

[msujew]

Thanks, looks quite nice. Just a few remarks, see below.

[msujew]

Thanks, I think this is good now.