Implement structured field and rule paths for violations

[jchadwick-buf]

Implements the changes needed to pass conformance after bufbuild/protovalidate#265.

This is basically a straight port of what is done in bufbuild/protovalidate-go#154, owing to the similarities between protovalidate-go and protovalidate-java. Unfortunately this means it inherits some of the trickier maneuvers needed to weave the right data into the right places. This version is also not as efficient as a result of differences between Go and Java protobufs, but effort was made to try to prevent big regressions in the case of successful validation.

Some of this is probably not as pretty as it could be. I'm open to improvements if there are any obvious things (I am certainly not a Java expert after all) but if possible I'd like to defer anything that would require major rethinking to down the road. (Happy to add TODOs for those, though.)

DO NOT MERGE until the following is done:

• Add structured field and rule paths to Violation protovalidate#265 is merged
• Dependencies updated to stable version release (waiting on manage module push)