Use records for updates

[prdoyle]

Rather than five separate submitXxx methods for five different kinds of updates, what if we had a single submitUpdate method that accepted an object describing the update? The records would look a bit like the ones here used by ReportingDriver.

This would be an even greater simplification than the one we envisaged in #42.

[prdoyle]

One problem with this idea is that Java 17 doesn't have type patterns in switch statements yet, which makes record destructuring cumbersome. I suppose we have a few options:

1. Create a bosk-java21 package containing components that are awkward to write without destructuring. The main one I've encountered so far is MirroringDriver which is mainly used for unit tests. We could even allow Java 21 in test code while remaining compatible with Java 17 in the library itself.
2. Create a destructuring helper class that would accept an update record and call one of five methods corresponding to the existing five BoskDriver methods. Use this until we're ready to drop Java 17 support. (This is a bit like a Visitor, which people tend to hate.)