Avoid use-after-return caused by double move

Summary:
Previously, `Result<T>`'s constructor used `std::move(val)` to initialize the
value. This resulted in an unnecessary extra move and destructor call on a
moved-from stack object, triggering an HWASAN stack tag mismatch when the
moved-from object was later destructed.

Replacing `std::move(val)` with just `val` avoids the extra move while
preserving correct semantics. This ensures only one move occurs and avoids
lifetime violations that can lead to tag mismatches under HWASAN.

Reviewed By: StefanBossbaly

Differential Revision: D76271359

Author: Tamir Duberstein

runtime/core/result.h

@@ -70,8 +70,8 @@ class Result final {
   /// Value copy constructor.
   /* implicit */ Result(const T& val) : value_(val), hasValue_(true) {}
 
-  /// Value move constructor.
-  /* implicit */ Result(T&& val) : value_(std::move(val)), hasValue_(true) {}
+  /// Value rvalue reference constructor.
+  /* implicit */ Result(T&& val) : value_(val), hasValue_(true) {}
 
   /// Result move constructor.
   /* implicit */ Result(Result&& rhs) noexcept : hasValue_(rhs.hasValue_) {