Add probing for netcoreapp3.1 tools and tps (#8543)

Author: KevinRansom

src/utils/CompilerLocationUtils.fs

@@ -256,7 +256,7 @@ module internal FSharpEnvironment =
         if typeof<obj>.Assembly.GetName().Name = "mscorlib" then
             [| "net48"; "net472"; "net471";"net47";"net462";"net461"; "net452"; "net451"; "net45"; "netstandard2.0" |]
         elif typeof<obj>.Assembly.GetName().Name = "System.Private.CoreLib" then
-            [| "netcoreapp3.0"; "netstandard2.1"; "netcoreapp2.2"; "netcoreapp2.1"; "netstandard2.0" |]
+            [| "netcoreapp3.1"; "netcoreapp3.0"; "netstandard2.1"; "netcoreapp2.2"; "netcoreapp2.1"; "netstandard2.0" |]
         else
             System.Diagnostics.Debug.Assert(false, "Couldn't determine runtime tooling context, assuming it supports at least .NET Standard 2.0")
             [| "netstandard2.0" |]