This commit adjusts the pretty printer for `std::coroutine_handle` based
on recent personal experiences with debugging C++20 coroutines:
1. It adds the `coro_frame` member. This member exposes the complete
coroutine frame contents, including the suspension point id and all
internal variables which the compiler decided to persist into the
coroutine frame. While this data is highly compiler-specific, inspecting
it can help identify the internal state of suspended coroutines.
2. It includes the `promise` and `coro_frame` members, even if
devirtualization failed and we could not infer the promise type / the
coro_frame type. Having them available as `void*` pointers can still be
useful to identify, e.g., which two coroutine handles have the same
frame / promise pointers.
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