Update dispute participation on active leaves update (#6303)

* Passed candidate events from scraper to participation

* First draft PR 5875

* Added support for timestamp in changes

* Some necessary refactoring

* Removed SessionIndex from unconfirmed_disputes key

* Removed duplicate logic in import statements

* Replaced queue_participation call with re-prio

* Simplifying refactor. Backed were already handled

* Removed unneeded spam slots logic

* Implementers guide edits

* Undid the spam slots refactor

* Added comments and implementers guide edit

* Added test for participation upon backing

* Round of fixes + ran fmt

* Round of changes + fmt

* Error handling draft

* Changed errors to bubble up from reprioritization

* Starting to construct new test

* Clarifying participation function rename

* Reprio test draft

* Very rough bump to priority queue test draft

* Improving logging

* Most concise reproduction of error on third import

* Add `handle_...