Remove defined marker

[ana-pantilie]

Fixes #2351

• removes TermLike.Defined entirely, definedness assumptions and checks are replaced by assumeDefined and isDefined
• makes the SideCondition available:
  • to the builtin evaluators
  • when matching
  • in the SMT translator/evaluator
• fixes both assumeDefined and isDefined to not ignore the values of maps

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Review checklist

The author performs the actions on the checklist. The reviewer evaluates the work and checks the boxes as they are completed.

• Summary. Write a summary of the changes. Explain what you did to fix the issue, and why you did it. Present the changes in a logical order. Instead of writing a summary in the pull request, you may push a clean Git history.
• Documentation. Write documentation for new functions. Update documentation for functions that changed, or complete documentation where it is missing.
• Tests. Write unit tests for every change. Write the unit tests that were missing before the changes. Include any examples from the reported issue as integration tests.
• Clean up. The changes are already clean. Clean up anything near the changes that you noticed while working. This does not mean only spatially near the changes, but logically near: any code that interacts with the changes!

[ana-pantilie]

@andreiburdusa @ttuegel Sorry, I realized I forgot to add a description to the PR. This made me notice that a few changes could be cleaned up a little and that I was missing some tests. I also fixed the conflicts with master.

[ttuegel]

Let's extract a helper function for these list elements.