azure-agent: add dependencies for its extensions

waagent's extension `Microsoft.OSTCExtensions.VMAccessForLinux` requires Python, otherwise it would be failed to install with the following error message in `/var/log/waagent.log`:

```
No Python interpreter found on the box
```

waagent's extension `Microsoft.CPlat.Core.RunCommandLinux` needs lsof, otherwise it would produce the following error message in `/var/log/waagent.log`:

```
/var/lib/waagent/Microsoft.Azure.Extensions.CustomScript-2.1.10/bin/custom-script-shim: line 60: lsof: command not found
```

nixos/modules/virtualisation/azure-agent.nix

@@ -241,7 +241,16 @@ in
       after = [ "network-online.target" "sshd.service" ];
       wants = [ "network-online.target" ];
 
-      path = [ pkgs.e2fsprogs pkgs.bash ];
+      path = [
+        pkgs.e2fsprogs
+        pkgs.bash
+
+        # waagent's Microsoft.OSTCExtensions.VMAccessForLinux needs Python 3
+        pkgs.python3
+
+        # waagent's Microsoft.CPlat.Core.RunCommandLinux needs lsof
+        pkgs.lsof
+      ];
       description = "Windows Azure Agent Service";
       unitConfig.ConditionPathExists = "/etc/waagent.conf";
       serviceConfig = {