### What happened?

I'm sorry I didn't weigh in on #11277 before it was merged. I'm thinking of this specifically for how to get this properly consumed by the bindings as per #11443 

2 things to bring the grid code more in line with other endpoints.
1. Use POST if there is info to send to an endpoint instead of query string
2. Return payload needs to be nested inside a `value` key.

Current implementation of file endpoint is:
```
POST /session/:sessionId:/se/file
file: <zippedFile>
```

To minimize confusion, I think the new feature should use `files` instead of `file`:
```
POST /session/:sessionId:/se/files
{fileName: <filename>}
```
and for #11458 
```
GET /session/:sessionId:/se/files
```

### How can we reproduce the issue?

```shell
n/a
```


### Relevant log output

```shell
n/a
```


### Operating System

n/a

### Selenium version

trunk

### What are the browser(s) and version(s) where you see this issue?

n/a

### What are the browser driver(s) and version(s) where you see this issue?

n/a

### Are you using Selenium Grid?

trunk
@Override
  public Session getSession(SessionId id) throws NoSuchSessionException {
    Require.nonNull("Session ID", id);
    SessionSlot slot = currentSessions.getIfPresent(id);
    if (slot == null) {
      throw new NoSuchSessionException("Cannot find session with id: " + id);
    }
    return createExternalSession(
      slot.getSession(),
      externalUri,
      slot.isSupportingCdp(),
      slot.isSupportingBiDi(),
      slot.getSession().getCapabilities());
  }
  @Override
  public TemporaryFilesystem getTemporaryFilesystem(SessionId id) throws IOException {
    try {
      return tempFileSystems.get(id, () -> TemporaryFilesystem.getTmpFsBasedOn(
          TemporaryFilesystem.getDefaultTmpFS().createTempDir("session", id.toString())));
    } catch (ExecutionException e) {
      throw new IOException(e);
    }
  }
  @Override
  public HttpResponse executeWebDriverCommand(HttpRequest req) {
    
    SessionId id = getSessionId(req.getUri()).map(SessionId::new)
      .orElseThrow(() -> new NoSuchSessionException("Cannot find session: " + req));
    SessionSlot slot = currentSessions.getIfPresent(id);
    if (slot == null) {