Use StructureProvider to populate navigator

[jtulach]

We at Enso are finally adding VSCode outline view into Enso VSCode extension:

• Enso language support with parser in VSCode, IGV, etc. enso-org/enso#7054

We had to write our own EnsoStructure provider. As the snapshots in the pull request demonstrate it is working fine in VSCode.

However: I also want it to work in NetBeans and IGV!

I see little point writing own navigator implementation and registering it in the Enso NBM. Especially when my original vision of the LSP API saw it as a way to hook into VSCode as well as NetBeans by writing one implementation and using it in both systems. This PR is my attempt to contribute to that vision.

• Existing lsp.client module now checks for presence of StructureProvider
• When found, it extracts the StructureElement hierarchy and builds nodes for the elements

The functionality is very close to the already existing functionality that works via LSP4J interfaces. Maybe there is a way to share the navigators - either by abstracting the functionality to common interfaces or by bridging (now deprecated) org.eclipse.lsp4j.SymbolInformation to StructureElement - what do you think? Abstracted common functionality in 47d411b and using it in edf081f

In any case, I'd be thankful if NetBeans recognized various LSP API providers and used them in the classical UI where appropriate. This is how NetBeans look with this PR and Enso4Igv NBM version v1.36.114:

[ppisl]

Good idea. At first glance, it seems good.

[dbalek]

Looks fine to me.

[lahodaj]

I am not much opposed to reusing the StructureProvider, but won't this mean we will get the dynamic LSP panel for all MIME types that have StructurePovider, in addition to their existing navigator panels?

[jtulach]

I am not much opposed to reusing the StructureProvider,

Great. I am glad you find the new dependency on lsp.api OK.

but won't this mean we will get the dynamic LSP panel for all MIME types that have StructureProvider,
in addition to their existing navigator panels?

That was the case. Maybe it is not that bad, especially when the StructureProvider is listed as the last option. But for now, I am disabling this StructureProvider view when there is normal Navigator/Panels/mime/type registration.

Since 7ef43e0 we display StructureProvider navigator only when there is no better navigator showing.