Migrate updatelog to abstract schema

And fixing the schema drift between mysql and postgres in this table by
changing field type of ul_key and ul_value from TEXT and TEXT to
VARCHAR(255) and BYTEA respectively.

The automatic generation is done with running generateSchemaSql.php
maintenance script. More info:
https://www.mediawiki.org/wiki/Manual:Schema_changes#Automatically_generated

Bug: T230428
Bug: T164898
Change-Id: Id785539d32546166d6f7a5c3cb1924f4841a2963