[Error] Distrobox is not location independent.

**Describe the bug**
`distrobox-enter` fails if location of distrobox-scripts changed on disk.

**To Reproduce**
This happened to me with Nix on Ubuntu when updating and the old distrobox version got GC'd from the nix store:

0. Assume a `nix`-enabled system
1. Get older distrobox: `nix-store -r /nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15`
2. Create a box `/nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15/bin/distrobox-create --name testbox --image ubuntu:20.04`
3. Enter box `/nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15/bin/distrobox-enter testbox` and leave again - works.
4. Stop box `/nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15/bin/distrobox-stop testbox`
5. Remove old distrobox: `nix-store --delete /nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15`
6. Get newer distrobox: `nix-store -r /nix/store/7nsxw7jggd33hrcbclgm5v13xds90r8w-distrobox-1.3.0`
7. Try to enter box `/nix/store/7nsxw7jggd33hrcbclgm5v13xds90r8w-distrobox-1.3.0/bin/distrobox-enter testbox` and observe reference to old version in failure message.
8. Get older distrobox again: `nix-store -r /nix/store/hcn0gjbb8xpl717pdp2bamzjcmspz3rp-distrobox-1.2.15`
9. Try to enter box `/nix/store/7nsxw7jggd33hrcbclgm5v13xds90r8w-distrobox-1.3.0/bin/distrobox-enter testbox` and observe things work.

**Expected behavior**
Distrobox should map its own location to a static path inside the container. (Distrobox already has great Nix support!)

**Logs**
Podman logs do not provide any useful data.

**Desktop (please complete the following information):**
- Are you using podman or docker? Podman
- Which version or podman or docker? Podman 4.1.0 (`/nix/store/76hhw9w196lpwmkyzh4c526ax6sb19gs-podman-wrapper-4.1.0/bin/podman`)
- Which version of distrobox? 1.2.15 and 1.3.0, see above