Adds a new 'key.retrieve_symbol_graph' option to the request. When set to 1 it
includes the JSON for a SymbolGraph containing a single node for the symbol at
the requested position.
This also extends the SymbolGraph library with a new entry point to get a graph
for a single symbol, and to additionally support type substitution to match the
existing CursorInfo behavior (e.g. so that when invoked on `first` in
`Array<Int>().first`, the type is given as `Int?` rather than `Element?`).
Resolves rdar://problem/70551509
This adjusts the tests for the difference between line endings on
different platforms. Windows uses CRLF while most Unicies use LF. This
was exposed during the update to the new LLVM snapshot.
`source.request.conformingmethods` is a new SourceKit request which
receives a source position and a list of protocol namses, returns a list
of methods whose return type conforms to the requested protocols.
rdar://problem/44699573
