**Why**
* in {T395928}, we are deleting many SecurePoll tables from production
* someday, we may need to reinstall them on a couple wikis. for example, to follow this procedure: https://www.mediawiki.org/wiki/Extension:SecurePoll#Enabling_local_elections_on_a_Wikimedia_wiki
**What**
* add 'securepoll' to the `switch` statement in CreateExtensionTables::execute() - https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/WikimediaMaintenance/+/refs/heads/master/createExtensionTables.php
* this script is likely to be used when SecurePoll is in one of the following two states:
* has 11 tables but is missing securepoll_log
* has 5 tables but is missing the 7 tables needed to do local elections (securepoll_cookie_match, securepoll_log, securepoll_options, securepoll_questions, securepoll_strike, securepoll_voters, securepoll_votes)
* algorithm suggestion: try to create all 12 tables, but handle a table already existing gracefully. the 12 tables are securepoll_cookie_match, securepoll_elections, securepoll_entity, securepoll_lists, securepoll_log, securepoll_msgs, securepoll_options, securepoll_properties, securepoll_questions, securepoll_strike, securepoll_voters, securepoll_votes
* these tables go on s1-8, not on x1