MIR: Add minimal interpreter

Context

This builds on changes from !10011 (merged), !10006 (merged) and !9999 (merged) adds a minimal interpreter on top of the generated AST. As in the preceeding merge requests, the implementation is limited to a small subset of instructions that can interpret the Fibonacci program from !9906 (merged).

Related: #6213 (closed)

Manually testing the MR

Please run cargo test interpret_test_expect to run the included test that runs the interpreter on an input stack and check the result. Use cargo test to run all the tests.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR