native kubernetes tls secrets incompatible with backup/exporter

The backup sidecar expect a secret to contain a ca.crt field (cert-manager style). The secret specified by serverSecretName is automatically mounted to the backup pod and the `/path/ca.crt` argument is passed to backup.

Native kubernetes tls secrets only contain `tls.key` and `tls.crt` fields so backup errors for file not found. To store the root CA an additional secret is required (rootCAs).

Currently, the secret specified by serverSecretName must be cert-manager style, and backup is unable to use the cert pool created by rootCAs otherwise backup will not function.
It's also likely exporter is affected.