[SVE][IR] Scalable Vector IR Type with pr42210 fix

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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363658 91177308-0d34-0410-b5e6-96231b3b80d8

test/Bitcode/compatibility.ll

@@ -917,6 +917,10 @@ define void @typesystem() {
   ; CHECK: %t7 = alloca x86_mmx
   %t8 = alloca %opaquety*
   ; CHECK: %t8 = alloca %opaquety*
+  %t9 = alloca <4 x i32>
+  ; CHECK: %t9 = alloca <4 x i32>
+  %t10 = alloca <vscale x 4 x i32>
+  ; CHECK: %t10 = alloca <vscale x 4 x i32>
 
   ret void
 }