[maglev] Re-enable stack-slot reuse by default

Looks like we hammered on the regalloc hard enough that this works again
🥳

Bug: v8:7700
Change-Id: I4f02417e069e3a6d89ca0c8c43ba165a502150e6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3899302
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83272}

src/flags/flag-definitions.h

@@ -453,7 +453,7 @@ DEFINE_BOOL(future, FUTURE_BOOL,
 DEFINE_BOOL(maglev, false, "enable the maglev optimizing compiler")
 DEFINE_BOOL(maglev_inlining, false,
             "enable inlining in the maglev optimizing compiler")
-DEFINE_BOOL(maglev_reuse_stack_slots, false,
+DEFINE_BOOL(maglev_reuse_stack_slots, true,
             "reuse stack slots in the maglev optimizing compiler")
 
 // We stress maglev by setting a very low interrupt budget for maglev. This