[#559] Update edsl-example tests

Description

Tests in code/cleveland/examples are quite outdated and use morley-1.2.0.

This MR updates the to use the latest version of the international test engine as well as testingEDSL.md doc which explains what is going on in these tests.

Note that this MR probably shouldn't be merged until we release a new version of morley that uses ghc-8.10.4.

Related issue(s)

Resolves #559 (closed)

✅ Checklist for your Merge Request

Related changes (conditional)

• Tests (see short guidelines)

  • 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:
    • Root README and other README.md files
    • Haddock
    • docs/
  • I updated changelog files of all affected packages released to Hackage if my changes are externally visible.

Stylistic guide (mandatory)

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

Problem: These tests are quite outdated now.

Solution: Update them to use the morley based on lts-17.3.