[Feat]: also `search` by annotations

[rchincha]

Is your feature request related to a problem? Please describe.

Currently, zot search uses repo, image and tags to index. It appears that annotations may be useful to index as well.

Scott Rigby [1:23 PM](https://cloud-native.slack.com/archives/C03EGRE4QGH/p1670448200988879)
That’s what I thought based on Steve’s comment in that #oras thread. Someone I know just mentioned they thought Zot already lets you discover by annotation somehow. Ok will think on this more and also raise the annotation filter idea in a dist spec issue for Helm chart artifacts use case. Maybe we could use artifactType for categorization/discovery, that just feels like an abuse

filed on behalf of @scottrigby

Describe the solution you'd like

Free search and/or annotation-based search must index annotations also.

Describe alternatives you've considered

No response

Additional context

No response