Increase "form_id" column from 32 to 128 characters

Right now we have a limit on the form_id column of 32 characters. While this arbitrary amount should be enough for most forms, in the Webform integration we may want to use a pseudo-nid placeholder for the form ID when creating a new node. The Webform Alt UI module uses a similar approach of assigning a timestamp as the form ID. This larger form ID should be more than enough for most situations.