Revert global.json and update devcontainer.json to install both .NET 9 and 10

Co-authored-by: eiriktsarpalis <[email protected]>

Author: Copilot

.devcontainer/devcontainer.json

@@ -3,7 +3,7 @@
 	"image": "mcr.microsoft.com/devcontainers/dotnet:1-8.0-jammy",
 	"features": {
 		"ghcr.io/devcontainers/features/dotnet:2": {
-			"version": "10.0"
+			"version": "9.0, 10.0"
 		},
 		"ghcr.io/devcontainers/features/node:1": {}
 	},

global.json

@@ -1,7 +1,7 @@
 {
   "sdk": {
-    "version": "9.0.100",
-    "rollForward": "latestFeature",
+    "version": "10.0.100-rc.1",
+    "rollForward": "minor",
     "allowPrerelease": true
   }
 }