Add ability to fetch user edits

CentralAuthUser->getGlobalEditCount implements this functionality.

Add the ability to check if the user exist (it could already have been renamed)

CentralAuthUser->getId can be used to check if a global user exists.

Check if user has any blocks

This kind of check was not available as a reusable function. I implemented this as a new method called CentralAuthUser->isBlocked in a patchset I'm currently working on. I'll reference this task in it when it's ready to review.

Add ability to fetch user Logs

These are shown in Special:GlobalRenameQueue currently using existing logging functionality implemented in LogEventsList found in Mediawiki core. I didn't confirm how well this works in a multi-wiki setup, but I can confirm this works fine with a single wiki (as-in rename logs that are stored on the same wiki as the queue page being used by the renamer).