feat(builder): Implement build cache for manifests & layers

Implements a cache that keeps track of:

a) Manifests that have already been built (for up to 6 hours)
b) Layers that have already been seen (and uploaded to GCS)

This significantly speeds up response times for images that are full
or partial matches with previous images served by an instance.

0 files changed, 0 insertions, 0 deletions