Simplify JSON schema, generation, copying and updating (#13427)

* Simplify JSON schema and only generate appsettings-schema.Umbraco.Cms.json

* Use Umbraco.JsonSchema.Extensions to dynamically add JSON schema references

* Move DependentUpon items to shared MSBuild props

* Update LangVersion to latest

* Update Umbraco.GitVersioning.Extensions to 0.2.0

* Remove JSON schemas on clean

* Remove Umbraco.JsonSchema.Core project

* Fix JSON schema nullability

* Ignore additional JSON schema files in template

* Update CompatibilitySuppressions.xml

* Remove GlobalSettings.UmbracoPath from JSON schema again

* Remove RemoveUmbracoJsonSchemaFiles target

* Update Umbraco.JsonSchema.Extensions to 0.2.0 and add weights

* Flatten generated JSON schema hierarchy

* Remove LicensesSettings from CMS codebase

* Change AdditionalParameters to IDictionary

templates/UmbracoProject/appsettings.Development.json

@@ -1,5 +1,5 @@
 {
-  "$schema": "./appsettings-schema.json",
+  "$schema": "appsettings-schema.json",
   "Serilog": {
     "MinimumLevel": {
       "Default": "Information"