Verify OpenTelemetry Collector images

[JamieMagee]

Extend the container image verification to the opentelemetry collector image (ghcr.io/open-telemetry/opentelemetry-collector-releases/opentelemetry-collector-contrib). Equivalent to the following command:

$ cosign verify \
   --certificate-identity=https://github.com/open-telemetry/opentelemetry-collector-releases/.github/workflows/base-release.yaml@refs/tags/v0.161.0 \
   --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
   ghcr.io/open-telemetry/opentelemetry-collector-releases/opentelemetry-collector-contrib:0.161.0

NOTE: the latest tagged release, 0.162.0, was manually published, so the verification WILL NOT WORK for that image. See open-telemetry/opentelemetry-collector-releases#1686 for more information