change client_info column_type to MEDIUMTEXT

[avirlrma]

Fixes #22362 Changed the column data-type for client_info from varchar(255) to MEDIUMTEXT in mysql event listener. This will allow for a larger payload to be stored, and is also inline with other columns(possibly big) in the table.

Release notes

( ) This is not user-visible or is docs only, and no release notes are required. ( ) Release notes are required. Please propose a release note for me. ( X ) Release notes are required, with the following suggested text:

# MySQL Event Listener 
* Change data type for client_info in mysql event listener to MEDIUMTEXT ({issue}`22362`)