remake of #4388

don't do it for every file added, as it's very slow
instead do the check at the end when all files are added.
this allows us to easily work with 10k+ files
fixes #4389

Co-authored-by: Antoine du Hamel <[email protected]>

instead make more specific methods for sub-validation
also rename validateTotals to validateAggregateRestrictions

- handle errors centrally so that we can limit the amount of toasts (informers) sent to the users (prevent flooding hundreds/thousands of them)
- introduce FileRestrictionError which is a restriction error for a specific file
- introduce isUserFacing field for RestrictionError

- show "%{count} additional restrictions were not fulfilled" for any restriction errors more than 4
- refactor/rename methods
- improve ghost logic/comments

- introduce new event "upload-start"  that can contain multiple files
- make a new patchFilesState method to allow updating more files
- unify "upload-start" logic in all plugins (send it before files start uploading)
- defer slicing buffer until we need the data
- refactor to reuse code

maybe it fixes the error

This reverts commit ff3e580.

merge it with RestrictionError

looks like the e2e tests are doing its job 👏