WIP: [TM-35] Implement PACKing

Description

Implements PACK interpretation. AFAIS all values/instructions are covered with tests.

Also I have fixed a couple of related bugs found when I wrote instructions sequences on Morley-Haskell for test suites, see commit history for details.

Related issue(s)

https://issues.serokell.io/issue/TM-35

✅ Checklist for your Merge Request

Related changes (conditional)

• Tests

  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • I checked whether I should update the docs and did so if necessary:
    • README
    • Haddock
    • docs/

Stylistic guide (mandatory)

• My commits comply with the following policy.
• My code complies with the style guide.