upload: Fix uploading the same file twice in the same session.

This commit fixes a bug where uploading the same file a second time
in the same browser session would appear to the user to stall with
`Uploading [filename]...` in the composebox.  This is because
`tus-js-client` makes a HEAD request to check for already-uploaded
files -- and, if found, that request is used in the `upload-success`
callback.  That left the callback with no response body to parse, to
know what URL to insert.

Store the `/user_uploads/...` URL in the file metadata after a
successful upload, and if the fingerprint matches a previous upload,
pull that URL (and filename, as it may have changed server-side) out
of the previous upload's metadata.

Co-authored-by: Shubham Padia <shubham@zulip.com>

package.json

@@ -18,6 +18,7 @@
     "@uppy/drag-drop": "^4.0.2",
     "@uppy/progress-bar": "^4.0.0",
     "@uppy/tus": "^4.1.5",
+    "@uppy/utils": "^6.1.3",
     "@zxcvbn-ts/core": "^3.0.1",
     "@zxcvbn-ts/language-common": "^3.0.2",
     "@zxcvbn-ts/language-en": "^3.0.1",