Add defining span to definition provider API

[mjbvz]

Supersedes #40045

Problem
See #10037

Proposal
Adds a new resolveDefinitionContext to DefinitionProvider. This allows a definition provider to return the defining symbol span.

[jrieken]

Based on current plan stretch for March esp. since we should understand what this means to ImplementationProviders, GoToTypeDefProvider

[mjbvz]

Yes good to consider those other providers too for the design of the api, but we only need the defining symbol range for the DefinitionProvider mouse ui currently. I think our goal here should be to come up with a general api pattern that we could also use in those other providers if needed