Remove the (unused) SIMDOperators module. (swiftlang#22530)

We originally planned to use this to hide some simd operators from the typechecker unless the user explicitly opted into having them but that scheme turned out to be ill-conceived, so we moved them
back into the stdlib. This change simply cleans up the empty vestigial module.

Author: stephentyrone

lib/Sema/CSStep.cpp

@@ -556,8 +556,8 @@ bool DisjunctionStep::shortCircuitDisjunctionAt(
   if (currentChoice->getKind() == ConstraintKind::CheckedCast)
     return true;
 
-  // If we have an operator from the SIMDOperators module, and the prior
-  // choice was not from the SIMDOperators module, we're done.
+  // If we have a SIMD operator, and the prior choice was not a SIMD
+  // Operator, we're done.
   if (currentChoice->getKind() == ConstraintKind::BindOverload &&
       isSIMDOperator(currentChoice->getOverloadChoice().getDecl()) &&
       lastSuccessfulChoice->getKind() == ConstraintKind::BindOverload &&

stdlib/public/CMakeLists.txt

@@ -56,11 +56,6 @@ if(SWIFT_BUILD_STDLIB)
   add_subdirectory(stubs)
   add_subdirectory(core)
   add_subdirectory(SwiftOnoneSupport)
-
-  # NOTE(compnerd) this must come after the SwiftOnoneSupport as the current
-  # cross-compilation support has to hand roll the import library setup which
-  # requires that the target is setup prior to use.
-  add_subdirectory(SIMDOperators)
 endif()
 
 if(SWIFT_BUILD_STDLIB OR SWIFT_BUILD_REMOTE_MIRROR)