Simplify how files are passed into the JS Client (and make consistent with Python Client)

[abidlabs]

Follow up from #7646:

If you look at the view API page for any endpoint that involves uploading a file, the file dictionary in the payload is very complex, e.g.:

This is technically correct, but it would be nice to wrap this in a helper function so users don't have to think about all of the fields. For the Python Client, we have a file() helper function that just takes in the path to the file and populates the rest of the fields accordingly, maybe we could do the same for the js client.

[pngwn]

Is this an artifact of the recorder or is this how it displays in all cases?

We used to fetch a file and pass that in as a blob/buffer.

[abidlabs]

In the other case, the code snippets involve blobs and fetch etc but I feel like that should be abstracted inside a file() method as well as discussed with @hannahblair

[pngwn]

Seems reasonable. We cant use file though as that is a built in. We will need to come up with another name.