Reland "Enable 31bit Smis everywhere"

This is a reland of c1bf25bb

Node bot will turn green after github.com/v8/node/pull/89/
has landed.

Original change's description:
> Enable 31bit Smis everywhere
>
> This is a experiment to see how performance is impacted. If we tank
> too much, we can revert this change.
>
> Change-Id: I01be33f5dd78aee6a5beecdc62adbaa6c3850eb1
> Bug: v8:8344
> Reviewed-on: https://chromium-review.googlesource.com/c/1355279
> Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#58157}

Bug: v8:8344
Change-Id: I85a6e5c479f1090f50df3df042571227279a0692
Reviewed-on: https://chromium-review.googlesource.com/c/1448314
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59251}

BUILD.gn

@@ -96,7 +96,7 @@ declare_args() {
 
   # Enable pointer compression (sets -dV8_COMPRESS_POINTERS).
   v8_enable_pointer_compression = false
-  v8_enable_31bit_smis_on_64bit_arch = false
+  v8_enable_31bit_smis_on_64bit_arch = true
 
   # Sets -dOBJECT_PRINT.
   v8_enable_object_print = ""