[User Story] Disassociate/delete signatures references to an image

[iamsamirzon]

User Need : As a user who accidently signed an image or have reasons to "unsign"/"remove' a signature, I need a mechanism to delete one or more signatures associated to an image

Desired Solution : A notation CLI command, similar to 'oras manifest delete" in ORAS CLI to remove/un-attach/delete signatures.

As is, for the OCI 1.1 based registries, users can delete the specific signature attached to an image.
However, for OCI 1.0 based registries, users have to do a lot of manual steps to remove one of the many signatures attached to an image