Add empty baselines to suppress api check

Author: pranavkm

src/Microsoft.AspNetCore.Mvc.RazorPages/baseline.netcore.json

@@ -0,0 +1,3 @@
+{
+  "AssemblyIdentity": "Microsoft.AspNetCore.Mvc.RazorPages, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60",
+}

src/Microsoft.AspNetCore.Mvc.Testing/baseline.netcore.json

@@ -0,0 +1,3 @@
+{
+  "AssemblyIdentity": "Microsoft.AspNetCore.Mvc.Testing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"
+}