[LV] Teach the vectorizer to cost and vectorize modf and sincospi intrinsics (#129064)

Follow on to #128035. It is a small extension to support vectorizing
`llvm.modf.*` and `llvm.sincospi.*` too.

This renames the test files from `sincos.ll` ->
`multiple-result-intrinsics.ll` to group together the similar tests
(which make up most of this PR).
diff --git a/llvm/lib/Analysis/VectorUtils.cpp b/llvm/lib/Analysis/VectorUtils.cpp
index dcfd3d5..ede0fca 100644
--- a/llvm/lib/Analysis/VectorUtils.cpp
+++ b/llvm/lib/Analysis/VectorUtils.cpp
@@ -73,6 +73,7 @@
   case Intrinsic::sin:
   case Intrinsic::cos:
   case Intrinsic::sincos:
+  case Intrinsic::sincospi:
   case Intrinsic::tan:
   case Intrinsic::sinh:
   case Intrinsic::cosh:
@@ -88,6 +89,7 @@
   case Intrinsic::maxnum:
   case Intrinsic::minimum:
   case Intrinsic::maximum:
+  case Intrinsic::modf:
   case Intrinsic::copysign:
   case Intrinsic::floor:
   case Intrinsic::ceil:
@@ -186,7 +188,9 @@
   case Intrinsic::ucmp:
   case Intrinsic::scmp:
     return OpdIdx == -1 || OpdIdx == 0;
+  case Intrinsic::modf:
   case Intrinsic::sincos:
+  case Intrinsic::sincospi:
   case Intrinsic::is_fpclass:
   case Intrinsic::vp_is_fpclass:
     return OpdIdx == 0;