Automatically updating the repl file with the fixtures

Unfortunately I don't know of a good way of loading the data from a `.json` file inside the `.repl` test file, so for now we would still need to manually update the `repl` file with the new data from the fixtures for future tests. (i.e. the `fixture-generator` will only update the `.json` files)

_Originally posted by @wwared in https://github.com/argumentcomputer/zk-light-clients/pull/216#pullrequestreview-2297702942_

Start by inspecting the fixture-generator and the existing flow between the generated .json fixtures and .repl test files. Confirm how the repl data is currently maintained, then define an update path whose completed output keeps the .repl fixtures synchronized whenever the generator runs.

Written by the indexing model from the issue text.