LSIF: GraphQL enhancements
Created by: efritz
This PR improves the LSIF GraphQL API:
- removes LSIFDump and LSIFJob as these can just get a node directly by identifier
- moves LSIFDump under Repository resolver
This PR also changes code structure a bit:
- a8n and codeintel resolvers are no longer assigned to
schemaResolver
, but to aOptionalResolvers
struct defined in the graphqlbackend package. This is necessary as the repositoryResolver (which is created directly in many places) also needs a reference to these optionally assigned resolvers (and there is no current way to pass them from the schema resolver as repository resolvers can be created independently).