Expose database replace in UI

[ ] rename files to more explicit eg 'file_search' 'file_replace' 'db_search' db_replace
[ ] run a search, make sure it has the placeholder column (existing code)
[ ] add some replace items to the csv
[ ] upload the same file again
[ ] unlock the session
[ ] if no replace then skip the record
[ ] if there is then do the replace on the record and store if the content ended up changing or not
[ ] have a progress bar and do the process inline in the web process not in a task (we may do this async in future)
[ ] when finished produce a summary of skipped vs replaced vs unmatched

catalyst / moodle-tool_advancedreplace