After the parent commit, the registry might contain prefixed images.
This commit adds the functionality to pull such prefixed image. Since we
rename the pulled image (to have a consistent name, from whichever
registry we might pull), remove the prefix as well so that it can be
used with other CI functionality (remove image, use in test, ...)

Examples for renaming:
- pull from internal_registry for x86
  internal_registry/oai-gnb:branchA => oai-ci/oai-gnb:branchA
- pull from internal registry for ARM with "arm_" prefix
  internal_registry/oai-gnb:arm_branchA => oai-ci/oai-gnb:branchA
- pull from x86 other registry (e.g., openshift)
  openshift/namespace/oai-gnb:branchA => oai-ci/oai-gnb:branchA