[EPIC] Add OCI Reference Type Support

[akashsinghal]

Add OCI reference type support based on latest additions to the opencontainers/distribution-spec. This will enable both existing ORAS referrers support as an extension as well as first class OCI referrers API.

• Add OCI Artifact Support #21
• Add Reference Type Support for OCI Manifest #22
• Add OCI Index Support for Reference Type #23

Optional:

• [Optional] Add Delete/GC support for OCI reference types #25

[shizhMSFT]

@wangxiaoxuan273 Let's follow up this EPIC.

[wangxiaoxuan273]

Sure!