it and describe space leaks

The implementation for `it` and `describe` can space leak thunk and `String`. Roughly speaking, both function takes the `String` for the name and convert it in a lazy way into a `Text` stored in the `Specify` or `Describe` node. However this value is only evaluated when the name of the `it` or `describe` is required. In a context where we dynamically build the test name (e.g. `it ("testCase" <> foo)`) it means that it maintains a thunk to the dynamic expression which can actually maintain alive a lot of objects. In a context were i have multiple thousand tests with a dynamic name, I observed up to a `GiB` of retained data which should not be there and this had a negative impact on the test suite performance (e.g. GC was painfully walking all of these values). Using the following workaround removed these `GiB` (replacing them by more compact `Text` reference) and reduce the runtime of my test suite by up to 2x. # Workaround One workaround for user are to force to WHNF the name before calling the `it`. In this context, it will still leak references to not compact `String`, but not to other object. Another workaround is to fore the name to a compact data (e.g. `Text`) and then convert it to `String`. The GC will only have to track a thunk and the `Text`. For example: ```haskell describe "hello" $ do let !name = "test" <> f x it (unpack name) $ ... ``` # Solution The `Text` value inside the `Scecify` or `Describe` node should be forced in the `it` or `describe` implementation. I'll submit an MR soon, but I'm opening this issue for reference.