Rationalize OCI image fetching logging

[dan-stowell]

Net effect

• Info+ log lines per cached image pull: ~6 -> 1
• Double-logged errors: 5-6 sites -> 0
• Log lines missing request context: 12 -> 2
• Ambiguous duplicate messages: 5 pairs -> 0
• Cache hit/miss metrics (OCIRegistryCacheEvents) fully preserved

deets

ocicache.go (library layer - log at boundary, not in library):

• Remove 7 Warning log lines from WriteManifestToAC and FetchManifestFromAC that were duplicated by callers in oci.go and ocifetcher.go
• Remove Info log on successful manifest write (normal path, no value)
• Downgrade manifest cache hit/miss from Info to Debug (metrics preserved)
• Add ctx to readThroughCacher for fire-and-forget cache write warnings (these are the only place these errors are logged)

oci.go (resolver - direct registry path):

• Downgrade 'Authenticating with registry' from Info to Debug (every pull)
• Downgrade 'Resolving image' from Info to Debug (every pull)
• Add ctx to 'Error fetching blob from cache' (was missing tracing)

ociregistry.go (HTTP mirror/registry):

• Differentiate two identical 'Error writing response body' messages

ociruntime.go (layer extraction):

• Add ctx to 4 filecache population log calls

ociconv.go (ext4 conversion):

• Add ctx to 3 Debug calls

[bduffany]

not a huge fan of the square-bracket prefix because this info is already logged automatically (and accessible in a nicer way imo)

• Expand the log entry in go/logs
• Find sourceLocation > file in the JSON payload
• Click the file name > "Add field to summary line"
• If you want to always see this info, you can make a go/ link since this state is stored in the URL (in the "summaryFields" param). We could consider updating go/logs to make it always visible as well

Should look like this:

Also during local development I believe we have the short filename prefix enabled by default (or if not, I think there is a flag to turn it on)

[dan-stowell]

ack, i'll remove