Revert "[JS IR] [runtime] Remove valueOf method from Long"

This reverts commit e13b6b2a90.

The significance of the breakage caused by the removal of `valueOf`
was underestimated.

#KT-50202 Open

js/js.translator/testData/box/native/long.kt

@@ -0,0 +1,16 @@
+// EXPECTED_REACHABLE_NODES: 1273
+// DONT_TARGET_EXACT_BACKEND: WASM
+// WASM_MUTE_REASON: UNSUPPORTED_JS_INTEROP
+// KJS_WITH_FULL_RUNTIME
+
+// Test that APIs expecting Number behave correctly with Long values.
+
+import kotlin.js.Date
+
+fun box(): String {
+    assertEquals("1970-01-01T00:00:00.000Z", Date(0L).toISOString())
+    assertEquals("10/4/1995, 12:00:00 AM", Date(1995, 9, 4, 0, 0, 0, 0L).toLocaleString("en-US"))
+    assertEquals(812764800000.0, Date.UTC(1995, 9, 4, 0, 0, 0, 0L))
+
+    return "OK"
+}