Add images entitlement for bake

[thompson-shaun]

Description

Follow-on work to add images entitlement for bake

[crazy-max]

For this entitlement we would probably want to rely on source policy:

• https://github.com/moby/buildkit/tree/master/sourcepolicy
• https://github.com/moby/buildkit/blob/master/docs/build-repro.md#reproducing-the-pinned-dependencies