Broken symlinks in /usr/lib/pressure-vessel/overrides/share/ with freedesktop.org runtime 23.08

While testing https://github.com/ValveSoftware/steam-runtime/issues/618 I noticed some unexpected broken symlinks which seem like they merit investigation.

On an Arch AMD/Mesa system, running a 23.08-based version of com.valvesoftware.Steam with a SLR test title (Ghostrunner demo):

1. 👍 All of /usr/lib/pressure-vessel/overrides/lib/** looks OK
2. 👍 /usr/lib/pressure-vessel/overrides/share/glvnd/egl_vendor.d/50_mesa.json correctly points to /run/parent/usr/lib/i386-linux-gnu/GL/glvnd/egl_vendor.d/50_mesa.json which exists
3. ❌ /usr/lib/pressure-vessel/overrides/share/glvnd/egl_vendor.d/1/50_mesa.json points to /run/parent/usr/lib/i386-linux-gnu/GL/glvnd/egl_vendor.d/50_mesa.json which doesn't exist
4. 👍 All of /usr/lib/pressure-vessel/overrides/share/vulkan/icd.d/ are regular files (because the originals contained absolute paths, which we have to rewrite) and their library_paths exist
5. 👍 MangoHud, MangoApp, fossilize in /usr/lib/pressure-vessel/overrides/share/vulkan/implicit_layer.d look OK
6. ❌ VK_LAYER_VALVE_steam_overlay_32 and VK_LAYER_VALVE_steam_overlay_64 appear twice each in implicit_layer.d, but otherwise look OK
7. 👍 /usr/lib/pressure-vessel/overrides/share/vulkan/implicit_layer.d/00.json points to /run/parent/usr/lib/x86_64-linux-gnu/GL/vulkan/implicit_layer.d/VkLayer_MESA_device_select.json
8. ❌ /usr/lib/pressure-vessel/overrides/share/vulkan/implicit_layer.d/01.json points to /run/parent/usr/lib/i386-linux-gnu/GL/vulkan/implicit_layer.d/VkLayer_MESA_device_select.json which doesn't exist (mitigation: if it existed, it would have the same content as the x86_64 flavour and be deduplicated)
9. 👍 similarly /usr/lib/pressure-vessel/overrides/share/vulkan/explicit_layer.d/0.json points to /run/parent/usr/lib/x86_64-linux-gnu/GL/vulkan/explicit_layer.d/VkLayer_MESA_overlay.json which exists
10. ❌ similarly /usr/lib/pressure-vessel/overrides/share/vulkan/explicit_layer.d/1.json points to /run/parent/usr/lib/i386-linux-gnu/GL/vulkan/explicit_layer.d/VkLayer_MESA_overlay.json which doesn't