Bump go-containerregistry and k8schain to pick up new cred helpers

Add installation instructions for OpenShift

This commit documents the steps required to install Chains on OpenShift.

Fix bug in uploading signatures to OCI

We should be using `SignedEntity` instead of `SignedImage` to account for manifest lists that may be signed by cosign.

Deprecate the `tekton-provenance` predicate format

For now, this will still work but we just print the error message.
It can be removed in a future release, and I removed all docs around it as well.

Add tutorial for generating signed provenance

This should help people set up signing OCI images and generating signed provenance for them.

Fix GIT_URL in release Pipeline

Fix auth bug for pushing images in release pipeline

Add in logs if the config is incorrect

Fix unit test & comment out default settings in deployment.yaml