unique type churn on file save intereferes with caching

[ceedubs]

Describe and demonstrate the bug

If you put this in your scratch file:

structural type Foo = Foo Nat

Foo.add : Foo -> Foo -> Foo
Foo.add = cases Foo n1, Foo n2 -> Foo (n1 + n2)

test> thing = test.verify do
  ensureEqual (Foo 3) (Foo.add (Foo 1) (Foo 2))

then it shows cached test results after the first save. But if you remove the structural (to make the type unique), it stops hitting the cache. I believe that this is because of unique type churn each time that you save the file. This means that it is also probably adding a lot of noise to the result cache.

Environment (please complete the following information):

• `ucm --version fc78d8a

Additional context

Discord discussion