compose: Support operating unprivileged on registry and oci

[cgwalters]

Closes: #5324

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

rust/src/compose.rs:264

• [nitpick] The variant name 'OciOrRegistry' may be ambiguous regarding whether it covers both OCI and registry transports. Consider renaming it to something more descriptive, such as 'UnprivilegedContainer' or similar.

OciOrRegistry,

.github/workflows/ci.yaml:279

• [nitpick] Ensure that 'test-oci.sh' provides adequate coverage for the unprivileged OCI/registry workflow and is maintained alongside changes to the transport handling.

sudo ./test-oci.sh

[cgwalters]

Nah this doesn't handle uid/gid right, it's going to require more work