Uploading many images causes app to freeze and not respond after crashing is fixed

Edit: Currently not testable as I cannot get to the point of uploads actually being queued due to a bug, this needs to be fixed first before being able to troubleshoot this further.

### Steps to reproduce
1. Have QA version of Nextcloud from https://github.com/nextcloud/android/pull/7340
2. Have a lot of uploads set to be auto uploaded
3. Wait

### Expected behaviour
File should get uploaded normally

### Actual behaviour
Files get uploaded and the app constantly gets ANR dialogues and freezes the Android system interface half the time.

### Can you reproduce this problem on https://try.nextcloud.com?
- Please create a test demo account and see if this still happens there.
- If yes, please open up a bug report
- If not, please verify server setup and ask for help on forum

### Environment data
Android version: 11

Device model: Google Pixel 2

Stock or customized system: stock

Nextcloud app version: 3.15.0

Nextcloud server version: 19.0.4

Reverse proxy:

### Logs
#### Web server error log
```
Insert your webserver log here
```

#### Nextcloud log (data/nextcloud.log)
```
Logcat logs (I think): [Nextcloud.txt](https://github.com/nextcloud/android/files/5567880/Nextcloud.txt)
```
**NOTE:** Be super sure to remove sensitive data like passwords, note that everybody can look here! You can use the Issue Template application to prefill some of the required information: https://apps.nextcloud.com/apps/issuetemplate