Reland^2 "[sparkplug] Enable sparkplug by default on desktop"

This is a reland of 0f79565b
which is a reland of 85e6c4b6
GC-stress issue was still flushing, now fixed for real with
https://crrev.com/c/3054117.

Relanding without changes.

TBR=verwaest@chromium.org

Original change's description:
> Reland "[sparkplug] Enable sparkplug by default on desktop"
>
> This is a reland of 85e6c4b6
> GC-stress issue was flushing, fixed with https://crrev.com/c/3048172.
> Relanding without changes.
>
> TBR=verwaest@chromium.org
>
> Original change's description:
> > [sparkplug] Enable sparkplug by default on desktop
> >
> > Bug: v8:11420
> > Change-Id: I07ac7f30b5ffffe40170ac15d5df0d3bf8a53523
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3041418
> > Auto-Submit: Leszek Swirski <leszeks@chromium.org>
> > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> > Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#75868}
>
> Bug: v8:11420
> Change-Id: I44ac0e4a5df07db79fa50db3134cdae3af41c88c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3053588
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#75916}

Bug: v8:11420
Change-Id: I24c7aea81ca58c339fc3bcc904663bdefb93106b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3054118Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#75926}

src/flags/flag-definitions.h

@@ -190,6 +190,13 @@ struct MaybeBoolFlag {
 #define ENABLE_SPARKPLUG false
 #endif
 
+#if ENABLE_SPARKPLUG && !defined(ANDROID)
+// Enable Sparkplug by default on desktop-only.
+#define ENABLE_SPARKPLUG_BY_DEFAULT true
+#else
+#define ENABLE_SPARKPLUG_BY_DEFAULT false
+#endif
+
 // Supported ARM configurations are:
 //  "armv6":       ARMv6 + VFPv2
 //  "armv7":       ARMv7 + VFPv3-D32 + NEON
@@ -647,7 +654,8 @@ DEFINE_INT(interrupt_budget_scale_factor_for_top_tier, 20,
 #else
 #define FLAG FLAG_READONLY
 #endif
-DEFINE_BOOL(sparkplug, false, "enable experimental Sparkplug baseline compiler")
+DEFINE_BOOL(sparkplug, ENABLE_SPARKPLUG_BY_DEFAULT,
+            "enable Sparkplug baseline compiler")
 DEFINE_BOOL(always_sparkplug, false, "directly tier up to Sparkplug code")
 DEFINE_BOOL(sparkplug_on_heap, false, "compile Sparkplug code directly on heap")
 #if ENABLE_SPARKPLUG