Record zstd:chunked format, and annotations, in BlobInfoCache

[mtrmac]

WIP, premature to review.

This should allow re-using on-registry zstd:chunked data on push, instead of re-pushing every time, or making the output not chunked.

This includes #2321, I’m filing it early just to have an URL to link to in #2189.

[mtrmac]

To test:

## CAREFUL, this is destructive
# podman rmi -a
# rm -f /var/lib/containers/cache/blob-info-cache-v1.sqlite 

- When asking for zstd:chunked, we can reuse an existing blob, incl. annotations
# podman pull quay.io/libpod/alpine
## compressses to chunked
# podman --log-level=debug push --compression-format zstd:chunked --force-compression quay.io/libpod/alpine localhost:50000/chunked
## image is chunked, has annotations
# skopeo inspect --raw docker://localhost:50000/chunked | jq .
## OLD: does not find a match, compresses again
## NEW: reuses existing layer
# podman --log-level=debug push quay.io/libpod/alpine localhost:50000/push2
## OLD: image is compressed using gzip
## NEW: image is chunked, has annotations
# skopeo inspect --raw docker://localhost:50000/push2 | jq .

- When asking for zstd, we can reuse zstd:chunked, incl. annotations
## OLD: Does not find a match, compressses again
## NEW: reuses existing layer
# podman --log-level=debug push --compression-format zstd --force-compression quay.io/libpod/alpine localhost:50000/zstd
## OLD: image is zstd, no annotations
## NEW: image is chunked, has annotations
# skopeo inspect --raw docker://localhost:50000/zstd | jq .

- A copy of zstd:chunked source does not recompress, but the data is only recorded as zstd
# rm -f /var/lib/containers/cache/blob-info-cache-v1.sqlite
## With BIC erased, does not find a match, compressses again
# skopeo --debug copy --dest-compress-format zstd:chunked docker://quay.io/libpod/alpine docker://localhost:50000/recompress
# rm -f /var/lib/containers/cache/blob-info-cache-v1.sqlite 
## Create a dir: copy of the chunked image (and establish blob existence)
# skopeo --debug copy docker://localhost:50000/recompress dir:chunked-dir
## A chunked -> chunked copy of a known-existing image reuses existing blobs
# skopeo --debug copy docker://localhost:50000/recompress docker://localhost:50000/chunked-copy2
## Pull from dir: instead of docker://, it is not partial = TOC-based, and just records general zstd data.
# podman --log-level=debug pull dir:chunked-dir
## See what is the image ID of the pulled image
# podman images
## Reuses an existing blob, does not repush
# podman --log-level=debug push --tls-verify=false 4819930274ea localhost:50000/repush
## The image is zstd (not chunked!) does not have annotations
# skopeo inspect --tls-verify=false --raw docker://localhost:50000/repush | jq .

[mtrmac]

Now ready for review. Podman tests are exercised in containers/podman#23397 .

@giuseppe PTAL ; Cc: @kolyshkin

[giuseppe]

Thanks!

LGTM

[rhatdan]

LGTM