fix(vscode): Update calls to check for dotnet installation

[ccastrotrejo]

This pull request primarily focuses on refactoring the way the .NET Core SDK validation is performed in the vs-code-designer application. The validateDotNetIsInstalled function has been moved to a different location and its usage has been updated in several files. The function's signature has also been modified to remove the message parameter.

• The message parameter was removed from the validateDotNetIsInstalled function. Instead, the message is now defined directly within the function.

• Imported the validateDotNetIsInstalled function from a new location.

• Removed the import of validateDotnetInstalled and imported the validateDotNetIsInstalled function from a new location.

• Updated the call to validateDotNetIsInstalled in the createStep method to match the new function signature.

• Updated the call to validateDotNetIsInstalled in the switchToDotnetProject function to match the new function signature.

• Removed the call to validateDotnetInstalled in the getLatestTemplates method.