Switch test runner to global.json (#11096)

* Switch test runner to global.json

* Update global.json

Author: Youssef1313

dotnet.config

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "10.0.100-rc.1.25420.111",
+    "version": "10.0.100-rc.2.25502.107",
     "allowPrerelease": true,
     "rollForward": "latestFeature",
     "paths": [
@@ -10,7 +10,7 @@
     "errorMessage": "The required .NET SDK wasn't found. Please run ./eng/common/dotnet.cmd/sh to install it."
   },
   "tools": {
-    "dotnet": "10.0.100-rc.1.25420.111",
+    "dotnet": "10.0.100-rc.2.25502.107",
     "runtimes": {
       "dotnet/x64": [
         "$(MicrosoftNETCorePlatformsVersion)"
@@ -23,6 +23,9 @@
       "version": "17.2"
     }
   },
+  "test": {
+    "runner": "Microsoft.Testing.Platform"
+  },
   "msbuild-sdks": {
     "Microsoft.DotNet.Arcade.Sdk": "11.0.0-beta.25522.101",
     "Microsoft.DotNet.Helix.Sdk": "11.0.0-beta.25522.101",