Always output fully-simplified states

[emarzion]

Fixes #2299

Update executionStrategy so that Simplify always appears after Rewrite. If execution is stopped by the depth limit, fully-simplified states will be printed for the user.

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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!

[ttuegel]

Suggested change

	deriving (Eq,Show)
	deriving (Eq, Show)

[ttuegel]

Using where would follow the style guide a bit better:

    step1 Stream.:> Stream.iterate id stepN
  where
    step1 =
        (Strategy.sequence . fmap Strategy.apply)
            [ Begin
            , Simplify
            , Rewrite
            , Simplify
            ]
    stepN =
        (Strategy.sequence . fmap Strategy.apply)
            [ Begin
            , Rewrite
            , Simplify
            ]

[ttuegel]

Let's write a function isLastSimplify :: Strategy Prim -> Bool in the same spirit as hasRewrite, so that we can cover all the cases better.

[ttuegel]

Please also have a look at our style guide.

[ttuegel]

I wrote a summary in the pull request this time, but please do that on your next pull request.