Update .NET SDK and C# language version

Bump .NET SDK version to 10.0.100 in global.json and set C# language version to 14.0 in Community.Toolkit.Common.props to enable new language features and maintain compatibility with the latest SDK.

Author: Sergio0694

build/Community.Toolkit.Common.props

@@ -20,7 +20,7 @@
 
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <LangVersion>12.0</LangVersion>
+    <LangVersion>14.0</LangVersion>
     <Nullable>enable</Nullable>
 
     <!--

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "9.0.306",
+    "version": "10.0.100",
     "rollForward": "latestFeature",
     "allowPrerelease": false
   }