Branch redirection drops query args

We currently use bots to provide the live links like this:

https://calypso.live/?branch=update/tiled-gallery-margins

It's often handy to provide links directly to a set up for testing, which may include path and additional query arguments. When the branch query is rewritten to the hash url, other query args are dropped. For example:

https://calypso.live/block-editor/post?branch=add/tiled-grid-package&flags=jetpack/blocks/beta

Winds up at (notice no `flags` arg):

https://hash-46d13ec811227b549777d82deb8a02736299c4ac.calypso.live/block-editor/post

Maintain unrecognized query args when redirecting.

Start by reproducing the branch redirect with the provided calypso.live URLs, including the path and flags query argument, then trace the branch-query rewrite in dserve. Done means the redirect reaches the hash URL while preserving unrecognized query arguments such as flags.

Written by the indexing model from the issue text.