media_filepath is not passed to storage providers

### Description

https://github.com/element-hq/synapse/blob/ab277b3e3ff6002536afbe29da268a52cf4cb0b6/synapse/media/media_storage.py#L206-L279

According to this implementation, the `media_filepath` is not passed to the storage providers as described in:
https://github.com/element-hq/synapse/blob/ab277b3e3ff6002536afbe29da268a52cf4cb0b6/synapse/media/storage_provider.py#L47-L54

This causes an issue when local storage is disabled, for example with https://github.com/matrix-org/synapse-s3-storage-provider/issues/162

### Steps to reproduce

- list the steps
- that reproduce the bug
- using hyphens as bullet points

### Homeserver

NOT RELEVANT

### Synapse Version

ab277b3e3ff6002536afbe29da268a52cf4cb0b6

### Installation Method

Other (please mention below)

### Database

NOT RELEVANT

### Workers

Single process

### Platform

NOT RELEVANT

### Configuration

NOT RELEVANT

### Relevant log output

```shell
NOT RELEVANT
```

### Anything else that would be useful to know?

I love usefull forms...

Start by reading synapse/media/media_storage.py at lines 206-279 and synapse/media/storage_provider.py at lines 47-54, then trace how storage providers are invoked. Done means the documented media_filepath reaches providers, including when local storage is disabled, with relevant tests passing.

Written by the indexing model from the issue text.