split out pbs-runtime module

These are mostly tokio specific "hacks" or "workarounds" we
only really need/want in our binaries without pulling it in
via our library crates.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/bin/proxmox-backup-api.rs

@@ -18,7 +18,7 @@ use proxmox_backup::config;
 fn main() {
     proxmox_backup::tools::setup_safe_path_env();
 
-    if let Err(err) = proxmox_backup::tools::runtime::main(run()) {
+    if let Err(err) = pbs_runtime::main(run()) {
         eprintln!("Error: {}", err);
         std::process::exit(-1);
     }