Properly handle files and sockets in extra mounts

[brandond]

Proposed Changes

Properly handle files and sockets in extra mounts

Also allows manually specifying HostPathType, in case an unhandled type is needed

Types of Changes

bugfix

Verification

See linked issue

• Test that a socket can be mounted into a pod:
  /run/systemd/journal/dev-log:/dev/log
• Test that an already existing file can be mounted into a pod:
  /usr/share/zoneinfo/Etc/UTC:/etc/localtime
/usr/share/zoneinfo/Etc/UTC:/etc/localtime:ro
• Test that a nonexistent file can be mounted into a pod, and will be created on first use:
  /tmp/example.txt:/tmp/example.txt:rw:FileOrCreate
/tmp/example.txt:/tmp/example.txt:ro:FileOrCreate

Testing

Linked Issues

• Validate hostpath is a directory for extra volume mounts #1793
• Clarify multiple volume mounts rke2-docs#173

User-Facing Change

Further Comments