v14: JSON schema tool improvements (#16035)

* Use require modifier instead of setting null-suppressed default values

* Only remove read-only properties when IgnoreReadOnlyProperties is set

* Obsolete UmbracoPath property and remove work-around for obsolete setter

tools/Umbraco.JsonSchema/Options.cs

@@ -3,5 +3,5 @@ using CommandLine;
 internal class Options
 {
     [Option("outputFile", Default = "appsettings-schema.Umbraco.Cms.json", HelpText = "Output file to save the generated JSON schema for Umbraco CMS.")]
-    public string OutputFile { get; set; } = null!;
+    public required string OutputFile { get; set; }
 }