client/remote: add support to specify port number

this adds the ability to add port numbers in the backup repo spec
as well as remotes, so that user that are behind a
NAT/Firewall/Reverse proxy can still use it

also adds some explanation and examples to the docs to make it clearer
for h2 client i left the localhost:8007 part, since it is not
configurable where we bind to

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/bin/proxmox_backup_client/benchmark.rs

@@ -225,7 +225,7 @@ async fn test_upload_speed(
 
     let backup_time = proxmox::tools::time::epoch_i64();
 
-    let client = connect(repo.host(), repo.user())?;
+    let client = connect(repo.host(), repo.port(), repo.user())?;
     record_repository(&repo);
 
     if verbose { eprintln!("Connecting to backup server"); }