### What?
Fixes client uploads when storage collection config has the `prefix`
property configured. Previously, it failed with "Object key was not
found".
### Why?
This is expected to work.
### How?
The client upload handler now receives to its props `prefix`. Then it
threads it to the server-side `staticHandler` through
`clientUploadContext` and then to `getFilePrefix`, which checks for
`clientUploadContext.prefix` and returns if there is.
Previously, `staticHandler` tried to load the file without including
prefix consideration.
This changes only these adapters:
* S3
* Azure
* GCS
With the Vercel Blob adapter, `prefix` works correctly.
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