Fix nested type splices in hie files

The issue is that when we compile a typed bracket we replace the splice
with HsSpliced (unTypeCode ...).

Then when computing types for

> [|| T $$(...) ||]

GHC is asked to compute the type of `T $$(..)`, which panics because
of the bogus type of T applied to `HsSpliced`, which is not type
correct.

The fix is to not attempt to compute the type for `HsSpliceE`
constructors if we come across them as they should have either been
already evaluated or lifted into a splice environment.

As part of the patch I made hie files traverse into the splice
environments so now we also get type information for things used inside
nested splices.

Fixes #21619