Add MaybeUninit memset test

Signed-off-by: Alex Saveau <saveau.alexandre@gmail.com>

src/test/codegen/issue-96274.rs

@@ -0,0 +1,11 @@
+// min-llvm-version: 15.0
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+use std::mem::MaybeUninit;
+
+pub fn maybe_uninit() -> [MaybeUninit<u8>; 3000] {
+    // CHECK-NOT: memset
+    [MaybeUninit::uninit(); 3000]
+}