Per T408177: [EPIC] Deprecate and remove mw.eventLog.id, the performer.active_browsing_session_token is defined using mw.eventLog.id.getSessionId(). Since both are defined in the EventLogging extension, we can rewrite the contextual attribute and remove the method in the same commit.

AC

• The internals of mw.eventLog.id are extracted and kept package-private
• The performer.active_browsing_session_token is rewritten in terms of the above
• mw.eventLog.id is removed
• Any mentions of mw.eventLog.id are tidied up
  • https://codesearch.wmcloud.org/search/?q=mw.eventLog.id&files=&excludeFiles=&repos=
  • https://global-search.toolforge.org/?q=%22mw.eventLog.id%22&namespaces=&title=