Sign kairos-agent and change release artifact

[Itxaka]

This patch changes the release artifact to be named kairos-agent instead of just kairos, so its clear what the archive is referring to.

Also adds keyless signing of the generated artifacts and provides both key/cert of ALL artifacts to validate the signature

Signed-off-by: Itxaka itxaka@spectrocloud.com

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #

[what-the-diff[bot]]

PR Summary

• Added OIDC Support for the release workflow, enhancing security and authentication.
• Implemented Cosign for signing artifacts, increasing trust and integrity of the software.
• Updated Goreleaser Configs to match project and naming conventions of KairosDB, providing better consistency.