Design observable logs configuration syntax

[jfallows]

As with other first class concepts in zilla.yaml, such as vaults and guards, we need a general concept of logs, independent of how they are stored locally or transmitted remotely, with more specific implementation for observability standards such as OpenTelemetry.

This can be used to detect Zilla internal errors triggered by external system inconsistencies, such as

• TCP server name not found (DNS)
• Kafka broker unreachable (network)
• Kafka topic name mismatch
• Kafka topic permissions
• Kafka topic message key required
• etc

[vordimous]

fixed by #755