core_arch: Add LoongArch LASX testcases

Author: heiher

crates/core_arch/src/loongarch64/lasx/mod.rs

@@ -11,3 +11,7 @@ mod generated;
 #[rustfmt::skip]
 #[unstable(feature = "stdarch_loongarch", issue = "117427")]
 pub use self::generated::*;
+
+#[rustfmt::skip]
+#[cfg(test)]
+mod tests;