rest-server: use hypers AddrIncoming for proxmox-backup-api

rest-server: use hypers AddrIncoming for proxmox-backup-api

this has a 'from_listener' (tokio::net::TcpListener) since hyper 0.14.5 in
the 'tcp' feature (we use 'full', which includes that; since 0.14.13
it is not behind a feature flag anymore).

this makes it possible to create a hyper server without our
'StaticIncoming' wrapper and thus makes it unnecessary.

The only other thing we have to do is to change the Service impl from
tokio::net::TcpStream to hyper::server::conn::AddStream to fulfill the trait
requirements.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>