Add a regression test for an unconstrained TransmuteFrom ICE

[johnproblems]

#151314: calling a function with an unconstrained TransmuteFrom obligation used to ICE with layout_of: unexpected type under the next-gen trait solver. It now reports type annotations needed (E0283) as expected. Fixed in #154991, but the issue was labelled E-needs-test and lacked a regression test, so this adds the original reproducer so it can't silently regress.

Closes #151314

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[johnproblems]

Thanks for catching that — you're right. I'd only checked that the original const repro now errors cleanly; I hadn't tried the type const form the diagnostic suggests, which still ICEs, so the issue isn't actually resolved. I've removed that test and kept just the next-solver TransmuteFrom one. Appreciate the review!

[reddevilmidzy]

Good, and please also change the PR title and description.