UI doesn't work satisfactory when adding 10k files

[mifi]

Steps to reproduce

1. Use a provider like Google Drive
2. have a folder with 10000 files
3. select the folder
4. click Add

Expected behavior

It should show some kind of progress to the user and then allow them use the UI and to upload the files within a reasonable amount of time

Actual behavior

It takes about 5 minutes to load all files (due to pagination on the api towards Google) this is expected and unavoidable - with #4388 this is OK because the user will be able to see what's happening

Then it takes about 2 minutes for all the addFile calls to finish

• maybe we can use core's addFiles instead (ok done!)

...
Adding remote file
loggers.js:15 [Uppy] [22:14:21] Added file: p599998.png, uppy-p599998/png-1e-image/png-327, mime type: image/png
...
about 20 000 lines
...

Then there's two errors that get spit out:

TransitionGroup.js:246 Uncaught TypeError: Cannot read properties of null (reading 'componentDidLeave')

Then the whole DOM/UI freezes for about 5 minutes and you can't click anything or scroll the list. Only the first few files are shown, without any thumbnail.

After 5 minutes you can scroll again, and you may now start the upload.

Maybe we should have an e2e test for this.

Note: Similar problem also for Drag/drop local files.

[mifi]

I just tried 11k files from remote provider (google drive) and now it actually works (after my big PR #4384 was merged). It takes about 7 seconds from the files are finished loading until they show up in the list. so UI is blocked for 7 seconds, and after that it's fully responsive (on Chrome). but I have a MBA M2, so maybe it's cheating. will test some more and try to get the block time down