Template cosign test

General MR

Install the BigBang Chart using OCI "Cosign" Verify.

Summary

Allow customer templates the option to install the OCI chart from a registry and verify the HelmRelease using cosign (and public key).

Relevant logs/screenshots

(Include any relevant logs/screenshots)

Linked Issue

big-bang/bigbang#1778 (closed)

Upgrade Notices

N/A. This is backwards compatible.