[ext-code-space] Enable external code space on x64 and desktop arm64

Perf Sheriffs: this CL might regress some benchmarks while improving
the others.

Bug: v8:11880
Change-Id: Iddaba0512100eedf61d8b106da0be0a08d273b67
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412072Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78743}

BUILD.gn

@@ -412,7 +412,9 @@ if (v8_enable_short_builtin_calls == "") {
       v8_current_cpu == "x64" || (!is_android && v8_current_cpu == "arm64")
 }
 if (v8_enable_external_code_space == "") {
-  v8_enable_external_code_space = false
+  v8_enable_external_code_space =
+      v8_enable_pointer_compression &&
+      (v8_current_cpu == "x64" || (!is_android && v8_current_cpu == "arm64"))
 }
 if (v8_enable_single_generation == "") {
   v8_enable_single_generation = v8_disable_write_barriers