This change removes the existing debug-web-client localapi endpoint
and replaces it with functions passed directly to the web.ServerOpts
when constructing a web.ManageServerMode client.
The debug-web-client endpoint previously handled making noise
requests to the control server via the /machine/webclient/ endpoints.
The noise requests must be made from tailscaled, which has the noise
connection open. But, now that the full client is served from
tailscaled, we no longer need to proxy this request over the localapi.
Updates tailscale/corp#14335
Signed-off-by: Sonia Appasamy <sonia@tailscale.com>