Clock reduction fix

[t-lohse]

Before, the clock reduction could not handle queries such as "refinement: A <= A" -i samples/json/AG where A has unused clocks within it. It would panic, trying to remove clocks on the left side of the expression, tat where actually found on the right side. This PR provides a fix to that.

Beyond that, when I created the tests, some other tests were panicking. This was because they expected an Ok from create_executable_query with a failure withing, but clock reduction compiles the system and returns the failure in Err if one is found. The reason for this is because these tests used ConsistencyExecutor, which has teh only struct implementing ExecutableQuery that took a SystemRecipe and compiled the system itself instead of taking a TransitionSystemPtr.
Therefore, I have refactored that, and a helper-function (json_run_query) in the tests so we can return the failure when performing clock reduction, instead of when executing the query. This involved a good portion of refactoring (hence the size of the PR), however it is mostly adapting the usage of said helper function

[seblund]

Looks good overall!

I left a few comments, but they are quick fixes if you agree.

Nice catch on the change for the ConsistencyExecutor, it is now instantiated exactly like the DeterminismExecutor, which is great. When we eventually add the specification and implementation executors we should probably introduce a helper function as they will all four will share the exact same instantiation code in extract_system_rep.rs.

[seblund]

LGTM

[seblund]

Still looks good :)