Extensions: Support versioned page in side-by-side view

Since AEM 6.3 the side-by-side version comparison works on the following path /content/versionhistory/[<tenant>/]/<userId>/<origininalPagePath> (for the versioned page on the right-hand side). That path should be supported by both ContextPathStrategy s (https://github.com/wcm-io/wcm-io-caconfig/blob/develop/extensions/src/main/java/io/wcm/caconfig/extensions/contextpath/impl/AbsoluteParentContextPathStrategy.java and https://github.com/wcm-io/wcm-io-caconfig/blob/develop/extensions/src/main/java/io/wcm/caconfig/extensions/contextpath/impl/RootTemplateContextPathStrategy.java) by subtracting two or three levels there (depending on whether a tenant is configured), i.e. the part versionhistory/[<tenant>/]/<userId> must be ignored when looking up the related CA configuration.