refactor(upload)!: take headers, method and body via an options object (#3613)

`upload(url, path, onProgress, { headers, method })` and
`download(url, path, onProgress, { headers, body })` replace the
positional optional arguments.

`headers` accepts both a `Map` and a plain object; previously a `Map`
was silently serialized as an empty object.

.changes/upload-options.md

@@ -0,0 +1,12 @@
+---
+"upload-js": major
+---
+
+**Breaking:** `upload` and `download` now take an `options` object as their last argument instead of positional `headers`, `method` and `body` arguments:
+
+```ts
+await upload(url, filePath, onProgress, { headers, method: HttpMethod.Put })
+await download(url, filePath, onProgress, { headers, body })
+```
+
+`headers` accepts both a `Map` and a plain object. Previously a `Map` was silently serialized as an empty object.