Turn regexp tier-up on by default to test performance and memory.

Change-Id: If546b1d2dc7019424383ce047ac4eb0410e954f0
Bug: v8:9566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1762289Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Ana Pesko <anapesko@google.com>
Cr-Commit-Position: refs/heads/master@{#63302}

src/flags/flag-definitions.h

@@ -1242,7 +1242,7 @@ DEFINE_UINT(serialization_chunk_size, 4096,
 DEFINE_BOOL(regexp_optimization, true, "generate optimized regexp code")
 DEFINE_BOOL(regexp_mode_modifiers, false, "enable inline flags in regexp.")
 DEFINE_BOOL(regexp_interpret_all, false, "interpret all regexp code")
-DEFINE_BOOL(regexp_tier_up, false,
+DEFINE_BOOL(regexp_tier_up, true,
             "enable regexp interpreter and tier up to the compiler")
 DEFINE_NEG_IMPLICATION(regexp_interpret_all, regexp_tier_up)