Add FSharpDisplayContext.WithShortTypeNames(bool) (dotnet#7651)

Author: auduchinok

src/fsharp/symbols/Symbols.fs

@@ -188,8 +188,12 @@ module Impl =
 
 type FSharpDisplayContext(denv: TcGlobals -> DisplayEnv) = 
     member x.Contents g = denv g
+
     static member Empty = FSharpDisplayContext(fun g -> DisplayEnv.Empty g)
 
+    member x.WithShortTypeNames shortNames =
+         FSharpDisplayContext(fun g -> { denv g with shortTypeNames = shortNames })
+
 
 // delay the realization of 'item' in case it is unresolved
 type FSharpSymbol(cenv: SymbolEnv, item: (unit -> Item), access: (FSharpSymbol -> CcuThunk -> AccessorDomain -> bool)) =

src/fsharp/symbols/Symbols.fsi

@@ -50,6 +50,8 @@ type [<Class>] public FSharpDisplayContext =
     internal new : denv: (TcGlobals -> Tastops.DisplayEnv) -> FSharpDisplayContext
     static member Empty: FSharpDisplayContext
 
+    member WithShortTypeNames: bool -> FSharpDisplayContext
+
 /// Represents a symbol in checked F# source code or a compiled .NET component. 
 ///
 /// The subtype of the symbol may reveal further information and can be one of FSharpEntity, FSharpUnionCase