fix all samples except prog-equiv

* symbolic backend test doesn't work still
* agent is broken because it relies on search and substitution
* prog-equiv is broken because it declares new constructors of sort Map

@andreiarusoaie we will not delay the merge trying to fix the symbolic backend, so if you want it to continue to work moving forward I suggest you fix it within unified-builtins2 while we are still waiting to merge.
@dlucanu your code in peq.k uses features of the framework that are being removed by this branch. You will no longer be able to declare new constructors of sorts Map, List, and Set. We will not delay the merge trying to fix this definition, so if you want it to continue to be regression tested moving forward, you will need to figure out how to fix the definition.