Flatpak specific SSH socket forwarding

As I've gathered, devpod creates an agent forwarding socket in the `/tmp` directory.

Flatpak has an option to create files that can be accessed by other applications through `xdg-run/app/${FLATPAK_ID}`.
For this instance, `xdg-run/app/sh.loft.devpod` can be used as the directory for the socket.

Then for other Flatpak applications, the permission `--filesystem=xdg-run/app/sh.loft.devpod` should be provided to access the sockets.

Though as of writing, devpod does not appear to have a configuration option for changing the forwarding socket directory.
I will also submit an issue in https://github.com/loft-sh/devpod in relation to this if the need arises.