Update GitHub Actions workflows to use .NET 8.0 SDK

- Aligned DOTNET_SDK_VERSION with the upgraded project framework across CI, publish, and test integration workflows.
- Ensured consistency in .NET versioning to facilitate correct environment setup for build and test processes.

.github/workflows/ci.yml

@@ -5,7 +5,7 @@ on: [push, pull_request]
 env:
   DOTNET_CLI_TELEMETRY_OPTOUT: true
   DOTNET_NOLOGO: true
-  DOTNET_SDK_VERSION: 7.0.x
+  DOTNET_SDK_VERSION: 8.0.x
   DOTNET_FRAMEWORK: net7.0
 
 jobs:

.github/workflows/publish.yml

@@ -6,8 +6,8 @@ env:
   CONFIGURATION: Release
   DOTNET_CLI_TELEMETRY_OPTOUT: true
   DOTNET_NOLOGO: true
-  DOTNET_SDK_VERSION: 7.0.x
-  NET_CORE_VERSION: net7.0
+  DOTNET_SDK_VERSION: 8.0.x
+  NET_CORE_VERSION: net8.0
   NET_FRAMEWORK_VERSION: net48
   PLUGIN_NAME: ASFFreeGames
 

.github/workflows/test_integration.yml

@@ -11,7 +11,7 @@ on:
 env:
   DOTNET_CLI_TELEMETRY_OPTOUT: true
   DOTNET_NOLOGO: true
-  DOTNET_SDK_VERSION: 7.0.x
+  DOTNET_SDK_VERSION: 8.0.x
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}