Experimental support for run/shell/exec of native OCI containers via OCI engine

[dtrudg]

Is your feature request related to a problem? Please describe.

Support execution of OCI images, in OCI native on-disk format, via runc OCI engine - but with the familiar Singularity CLI.

Describe the solution you'd like

Target support for the following subset of options/flags in 3.11.

--bind mounts
--mount mounts
Default home and cwd mounts
Namespace requests
--env / --envfile / SINGULARITYENV_
--apply-cgroups
--rocm / --nv (binding method)
--fakeroot

No handling of --network, --security options etc.

Additional context See https://sylabs.io/2022/02/singularityce-4-0-and-beyond

Sub-tasks

• [x] #1021
• [ ] #1022
• [ ] #1023
• [ ] #1024
• [ ] #1025
• [ ] #1026
• [ ] #1027
• [ ] #1028
• [ ] #1029
• [ ] #1030
• [ ] #1031
• [ ] #1032
• [ ] #1033
• [ ] #1034
• [ ] #1035
• [ ] #1036