Verify public-private key pair obtained from vault used for TLS handshake

[jfallows]

Describe the desired outcome from the user's perspective
As devops, I want to detect when zilla is misconfigured such that TLS private key does not match public key.

Acceptance criteria

• Verify public-private key pair
• Log event if public-private key pair is invalid

Additional context
By performing this check in the tls binding where the key pair is used, then each vault does not need to reimplement.

Note: there are at least two ways to approach this.
https://stackoverflow.com/questions/49426844/how-to-validate-a-public-and-private-key-pair-in-java