Upgrade CertHandler to use TLS certificates v4

[Abuelodelanada]

Enhancement Proposal

There is a brand new version of the tls_certificates lib with Python API changes.

We should investigate how to modify CertHandler in order to use that new lib version.

[gruyaume]

TLS Lib v4 automatically takes care of:

• Private key management
• CSR creation
• Certificate request and renewals

It should render CertHandler unnecessary at this point.

[lucabello]

We should update this issue with all the PRs for all repos where we do this update. When all are completed, we can deprecate CertHandler and close this issue.

[lucabello]

Reference:

• https://github.com/canonical/cos-coordinated-workers/pull/13/files
• https://github.com/canonical/opentelemetry-collector-k8s-operator/blob/0edd65b411585b544c6455ffeecfdd2cdcdb2953/src/integrations.py#L381 (without events)