Implement new `SymbolInformation` fields in the SCIP backend

[nicolas-guichard]

sourcegraph/scip/issues/154 added support for a number of new fields in SCIP's SymbolInformation:

• kind
• display_name
• signature_documentation
• enclosing_symbol (what was originally proposed as owner or parent in the linked issue)

/pull/15806 recently updated scip to 0.3.1 which makes those new fields available to rust-analyzer. They are currently always defaulted.

@donsbot you said you wanted to add support for those in rust-analyzer, do you still plan on doing that?
If not I'm also interested in working on that, for use in Searchfox.

[donsbot]

Go for it!