Revert r363658 "[SVE][IR] Scalable Vector IR Type with pr42210 fix"

We saw a 70% ThinLTO link time increase in Chromium for Android, see
crbug.com/978817. Sounds like more of PR42210.

> Recommit of D32530 with a few small changes:
>   - Stopped recursively walking through aggregates in
>     the verifier, so that we don't impose too much
>     overhead on large modules under LTO (see PR42210).
>   - Changed tests to match; the errors are slightly
>     different since they only report the array or
>     struct that actually contains a scalable vector,
>     rather than all aggregates which contain one in
>     a nested member.
>   - Corrected an older comment
>
> Reviewers: thakis, rengolin, sdesmalen
>
> Reviewed By: sdesmalen
>
> Differential Revision: https://reviews.llvm.org/D63321

llvm-svn: 364543