Reland "[wasm] Enable --wasm-opt"

This is a reland of 757f0431

There was a bug in a TurboFan optimization that was fixed in
https://chromium-review.googlesource.com/c/v8/v8/+/2504250

Original change's description:
> [wasm] Enable --wasm-opt
>
> This CL enables basic optimizations in TurboFan for WebAssembly code,
> like dead code elimination (DeadCodeElimination), constant folding
> (MachineOperatorReducer), and control flow optimizations
> (CommonOperatorReducer).
>
> These optimizations were disabled originally to improve startup time,
> at the expense of slower generated code. However, with Liftoff as the
> baseline compiler, startup time is not so important anymore for
> TurboFan.
>
> R=clemensb@chromium.org
> CC=manoskouk@chromium.org
>
> Change-Id: I2a81f66929c43fbbdfc3625359772c8ea0f2235f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2488684
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#70691}

Change-Id: Ia3f6f48649c329b9a49e038264dd12f7d872d275
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2504265Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70871}

src/flags/flag-definitions.h

@@ -863,7 +863,7 @@ DEFINE_BOOL(wasm_staging, false, "enable staged wasm features")
 FOREACH_WASM_STAGING_FEATURE_FLAG(WASM_STAGING_IMPLICATION)
 #undef WASM_STAGING_IMPLICATION
 
-DEFINE_BOOL(wasm_opt, false, "enable wasm optimization")
+DEFINE_BOOL(wasm_opt, true, "enable wasm optimization")
 DEFINE_BOOL(
     wasm_bounds_checks, true,
     "enable bounds checks (disable for performance testing only)")