…pe (like a SkolemType)

When the SkolemType appears as the prefix of a TypeRef, we avoid it by going
using `qualifier` which is defined in QuotesImpl to widen skolem, but skolems
can appear in any position, and so before this change we would get a compiler
crash in the added test case where the skolem appears as the prefix of a
TermRef.

We fix this by adding fallback cases in the quotes pretty-printer, now for the
test case we get:

    Test.f.ho(((arg: <<SkolemType(693709097) does not have a corresponding extractor> does not have a source representation>.x.type) => arg))

Which isn't great, but better than a crash.

Maybe we should run `Type#deskolemized` on a type before trying to print it in
SourceCode/Extractors, but currently these files are intentionally defined to
not depend on compiler internals and do not have a `Context` so we cannot even
call `deskolemized` on them.

Alternatively, maybe SkolemType should be a tasty-reflect constructor but that
would also be a pretty big change.

[Cherry-picked 0ee8762][modified]