Add VSA signing and unit tests #2597

Namespace: <a href="https://detailurl.setting.custom-console-url-namespace.is.not.configured" rel="nofollow">rhtap-contract-tenant
PipelineRun: <a href="https://konflux-ui.apps.stone-prd-rh01.pg1f.p1.openshiftapps.com/ns/rhtap-contract-tenant/pipelinerun/cli-main-on-pull-request-q6rcd" rel="nofollow">cli-main-on-pull-request-q6rcd

Success

Red Hat Konflux/cli-main-on-pull-request has successfully validated your commit.

Status	Duration	Name
🟢 Succeeded	6 seconds	init
🟢 Succeeded	18 seconds	clone-repository
🟢 Succeeded	2 minutes	prefetch-dependencies
🟢 Succeeded	3 minutes	build-container
🟢 Succeeded	5 seconds	build-image-index
🟢 Succeeded	6 seconds	apply-tags
🟢 Succeeded	19 seconds	sast-shell-check
🟢 Succeeded	10 seconds	rpms-signature-scan
🟢 Succeeded	8 seconds	push-dockerfile
🟢 Succeeded	1 minute	clamav-scan
🟢 Succeeded	1 minute	build-source-image
🟢 Succeeded	24 seconds	deprecated-base-image-check
🟢 Succeeded	37 seconds	clair-scan
🟢 Succeeded	10 seconds	build-tekton-bundle
🟢 Succeeded	27 seconds	ecosystem-cert-preflight-checks
🟢 Succeeded	34 seconds	sast-snyk-check
🟢 Succeeded	19 seconds	sast-unicode-check
🟢 Succeeded	8 seconds	show-sbom