Spike - Plugin API versioning

[jflo]

As our plugin ecosystem gets richer and more sophisticated, we are going to need to be able to accommodate varying degrees of plugin compatibility.

Plugin architectures implemented in Java should be a well understood problem, and there is likely lots of prior-art on the subject. We should collect the top 2-3 most common approaches, and review them for compatibility with our needs.

Time box this to about 24 hours.

Judgement criteria:

• anti-fragility; avoid breaking besu, as well as past plugins.
• maleability; how best to maximize decoupling to avoid placing restrictions on the rest of the besu codebase
• UX: what patterns allow plugin developers to easily implement configurability, observability and ease of documentation.
• upgradeability; when anti-fragility cannot be met, what upgrade paths can be provided with the lowest friction to plugin devs.