Remove `/data/local-files/` path prefix requirement for local storage

**Describe the bug**
When adding local storage, label-studio requires them to be stored at `/data/local-files`. When running OSX, this is not always possible (depending on the version). Also it is asking for an absolute path, which implicates not having prefixes.

**To Reproduce**
1. Add a new project
2. Go to http://localhost:8080/projects//settings/storage and add a new storage
3. select "local storage" and enter the "absolute path".
4. Click "Save & Sync"
5. Navigate to http://localhost:8080/projects//data?tab=2 and click one of the tasks
6. Inspect the error:
```
There was an issue loading URL from $image value

Things to look out for:

URL is valid
URL scheme matches the service scheme, i.e. https and https
The static server has wide-open CORS, [more on that here](https://labelstud.io/guide/storage.html#Troubleshoot-CORS-and-access-problems)
Technical description:
URL: [/data/local-files/?d=Users/rot0004f/.code/setpoint/setpoint/transcoder/dataset/images/train/frame_00000.jpg](http://localhost:8080/data/local-files/?d=Users/rot0004f/.code/setpoint/setpoint/transcoder/dataset/images/train/frame_00000.jpg)
```

**Expected behavior**
The configured absolute path is where Label Studio looks for the files.

**Screenshots**

**Environment (please complete the following information):**
- OS: OSX Tahoe
- Label Studio: v1.21.0