Raise warning to errors once decommissioning of deprecated packages is near

There is already a WARNING raised in case a deprecated API is used in the code via the analyser https://github.com/apache/sling-org-apache-sling-feature-extension-apiregions/blob/master/src/main/java/org/apache/sling/feature/extension/apiregions/analyser/CheckDeprecatedApi.java. This is often not noticed by developers, so there should be configuration parameter to raise this warning to an error (failing the build) in case the decommissioning date according to https://experienceleague.adobe.com/docs/experience-manager-cloud-service/release-notes/deprecated-apis.html?lang=en comes closer.
This probably requires publishing that information in a machine-readable way. The configuration parameter should allow to define a time span from which on the WARN is raised to an ERROR automatically (by default 4 weeks prior to removal).

Start by reading src/main/java/org/apache/sling/feature/extension/apiregions/analyser/CheckDeprecatedApi.java and the Adobe deprecated APIs page linked in the issue. Determine how removal dates could be published in machine-readable form and how a configuration threshold should affect the existing warning. Done means deprecated API use becomes an error within the configured default or custom time span before removal.

Written by the indexing model from the issue text.