Design a way to use the Rust view server with mock consensus integration tests

[hdevalence]

Is your feature request related to a problem? Please describe.

Currently we are trying to expand the capability of our state machine tests, going depth-first: writing a few, targeted tests that incrementally expand the capability of the test harness and allow us to discover requirements.

These tests are intended to exercise functionality end to end, including client logic. Currently we do this with the MockClient, a minimal reference implementation of key Penumrba client logic.

However, a benefit and limitation of this approach is that we cannot automatically generate transaction plans, because the MovkClient cannot be used with a Planner. This is a benefit because we can write tests that are very precise about their state changes and do not rely on a much larger mass of code, but a limitation because more complex test logic would prefer to use the planner.

Additional context here: https://github.com/penumbra-zone/penumbra/pull/3891#discussion_r1503536584

Describe the solution you'd like

There are a lot of moving pieces and a lot of context to consider to figure out the right design. @cratelyn and I should pair to explore the best path forward.

[cratelyn]

@hdevalence i prepared a scaffold in #3958, taking a small preparatory step towards using MockClient with Planner::plan().

[cratelyn]

#3896 is loosely related to this work.

[cratelyn]

#4081 has been fixed by #4312, so i am planning to pick this work back up.