Provides support for running Jepsen tests in Antithesis. Provides an RNG,
lifecycle hooks, and assertions.

## Randomness

You should wrap your entire program in `(with-rng ...)`. This does nothing in
ordinary environments, but in Antithesis, it replaces the jepsen.random RNG
with one powered by Antithesis.

## Lifecycle

Call `setup-complete!` once the test is ready to begin--for instance, at the
end of Client/setup. Call `event!` to signal interesting things have
happened.

## Assertions

Assertions begin with `assert-`, and take an expression, a message, and data
to include if the assertion fails. For instance:

  (assert-always! (not (db-corrupted?)) "DB corrupted" {:db "foo"})

## Wrappers

Wrap your test map in `(a/test test-map)`. This wraps both the client and
checkers with Antithesis instrumentation. You can also do this selectively
using `checker` and `client`.

Antithesis' Test Composer drives Jepsen by calling shell scripts, which
communicate with the test via a control directory full of FIFOs. Each FIFO
represents a single test composer action. They work like this:

1. Test composer calls a script to do something.
2. Script creates a fifo like /run/jepsen/op-1234, and blocks on it.
3. Jepsen, watching /run/jepsen, detects the new fifo
4. Jepsen fires off an invocation
5. The operation completes
6. Jepsen writes the results of the operation to /run/jepsen/invoke_1234
7. Jepsen closes the FIFO
8. The shell script prints the results out and exits
9. The test composer receives the results

The types of commands are:

- `op-123`: Runs a single operation from the generator
- `check`: Wraps up the test's :generator, runs :final-generator, and
           checks the history.

This namespace provides the Jepsen-side infrastructure for watching the FIFO
directory, a test runner like `jepsen.core/run!`, and a CLI command called
`antithesis` which works like `test`, but uses our runner instead.