LibJS: Inline fast case for Value::to_{boolean,number,numeric,primitive}

These functions all have a very common case that can be dealt with a
very simple inline check, often avoiding the need to call an out-of-line
function. This patch moves the common case to inline functions in a new
ValueInlines.h header (necessary due to header dependency issues..)

8% speed-up on the entire Kraken benchmark :^)

Userland/Libraries/LibJS/Runtime/ValueInlines.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Completion.h>
+#include <LibJS/Runtime/Value.h>
+
+namespace JS {
+
+inline bool Value::to_boolean() const
+{
+    // OPTIMIZATION: Fast path for when this value is already a boolean.
+    if (is_boolean())
+        return as_bool();
+
+    return to_boolean_slow_case();
+}
+
+inline ThrowCompletionOr<Value> Value::to_number(VM& vm) const
+{
+    // OPTIMIZATION: Fast path for when this value is already a number.
+    if (is_number())
+        return *this;
+
+    return to_number_slow_case(vm);
+}
+
+inline ThrowCompletionOr<Value> Value::to_numeric(VM& vm) const
+{
+    // OPTIMIZATION: Fast path for when this value is already a number.
+    if (is_number())
+        return *this;
+
+    return to_numeric_slow_case(vm);
+}
+
+inline ThrowCompletionOr<Value> Value::to_primitive(VM& vm, PreferredType preferred_type) const
+{
+    if (!is_object())
+        return *this;
+    return to_primitive_slow_case(vm, preferred_type);
+}
+
+}