[main-next] Net9/Net8 support

[tl-Roberto-Mancinelli]

Introduced new main next (2.0 version) with net9/net8 support.
Updated CI/cake to latest version
Removed old dep.
Minor improvements/Fix vulnerabilities

This pull request includes several updates to dependencies, workflow configurations, and code cleanup. The most important changes involve updating the .NET version, modifying workflow files, and cleaning up the build.cake file.

Dependency and tool updates:

• Updated the cake.tool version from 1.3.0 to 5.0.0 in .config/dotnet-tools.json and .github/workflows/build.yml and .github/workflows/publish.yml files. [1] [2] [3]
• Updated various tool versions in build.cake, including dotnet-reportgenerator-globaltool, coveralls.net, and dotnet-sonarscanner.

Workflow configuration updates:

• Updated the GitHub Actions workflow files to use newer versions of actions and to set up .NET 9.0 and 8.0. [1] [2]
• Changed the runs-on environment from ubuntu-22.04 to ubuntu-24.04 in both build.yml and publish.yml workflow files. [1] [2]

Code cleanup and refactoring:

• Removed unused imports and cleaned up the code in several files, including HomeController.cs, ErrorViewModel.cs, and various model files. [1] [2] [3] [4] [5] [6] [7] [8]
• Simplified and updated method calls in build.cake, such as replacing DotNetCoreBuild with DotNetBuild and DotNetCoreTest with DotNetTest. [1] [2] [3] [4]

Project and configuration updates:

• Updated the target framework to net9.0 in examples/MvcExample/MvcExample.csproj.
• Updated the .NET SDK version to 9.0.100 in global.json.

View files updates:

• Added @using Microsoft.AspNetCore.Mvc.TagHelpers to several view files to enhance tag helper support. [1] [2] [3] [4] [5]