[.NET] Updating to .NET 9 (#9539)

The focus of these changes is to update the current .NET SDK and targets to
support .NET 9.

eng/pipelines/templates/steps/install-dotnet.yml

@@ -23,7 +23,7 @@ steps:
       # https://github.com/Azure/azure-sdk-tools/pull/5405#discussion_r1105006774
       # https://github.com/Azure/azure-sdk-tools/pull/5405
       packageType: sdk
-      version: 9.0.x
+      version: 8.0.x
       # performMultiLevelLookup comes into play when given .NET executable target runtime is different
       # than the installed .NET SDK. Without this, such runtime would not be found.
       performMultiLevelLookup: true

global.json

@@ -3,7 +3,7 @@
     "Microsoft.Build.Traversal": "3.2.0"
   },
   "sdk": {
-    "version": "8.0.302",
+    "version": "9.0.101",
     "rollForward": "feature"
   }
 }

tools/snippet-generator/Azure.Sdk.Tools.SnippetGenerator.Tests/Azure.Sdk.Tools.SnippetGenerator.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFrameworks>net8.0;net9.0</TargetFrameworks>
         <IsPackable>false</IsPackable>
     </PropertyGroup>
 

tools/snippet-generator/Azure.Sdk.Tools.SnippetGenerator/Azure.Sdk.Tools.SnippetGenerator.csproj

@@ -2,7 +2,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <Description>Generates code snippets for readmes in the azure-sdk-for-net repo.</Description>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net8.0;net9.0</TargetFrameworks>
     <PackAsTool>true</PackAsTool>
     <ToolCommandName>snippet-generator</ToolCommandName>
     <VersionPrefix>1.0.0</VersionPrefix>