Adopt rjsf 5

[bollwyvl]

Elevator Pitch

rjsf 5 is in beta. Skip the 4.x line entirely and support 5.x as part of the breaking changes represented in #87.

Motivation

5 improves the long-term supportability of downstreams, as it decouples validation from a hard dependency on a specific version of ajv (even if practically it doesn't have any other implementations yet). It also makes certain customizations easier, such as templates which might make #52 easier.

Design Ideas

• see migration guide.
• time permitting, we could already start kicking the tires with the beta releases
  • hanging tight for an rc might be a better use of time
• perhaps work this into a more thorough pr to jupyterlab, which still has a lot of razor-sharp edges for downstreams to use effectively

[bollwyvl]

Perhaps the cleanest path to this would be to separate @deathbeds/jupyterlab-rjsf to a separate package. This could then also consume @deathbeds/wxyz-json-schema-form, and resurrect some of the standalone functionality from this stale branch.