Upon further evaluation, we've unfortunately misinterpreted the purpose of progress interface, where the message passed via the interface should just be an operation string. Hence there is no requirement for this string to be a complex message string.

Definition of Done:

• Revert the changes of WT-8396.
  • This is to be done manually since there are some other improvements in the commit which shouldn't be reverted. We should only revert the changes relating to '__wt_progress'.