[regexp] Stage match indices.

Bug: v8:9548
Change-Id: Id6be43433b12733e39db712559715ba30e681059
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1935207
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65218}

src/flags/flag-definitions.h

@@ -207,7 +207,6 @@ DEFINE_IMPLICATION(harmony_import_meta, harmony_dynamic_import)
   V(harmony_string_replaceall, "harmony String.prototype.replaceAll") \
   V(harmony_regexp_sequence, "RegExp Unicode sequence properties")    \
   V(harmony_weak_refs, "harmony weak references")                     \
-  V(harmony_regexp_match_indices, "harmony regexp match indices")     \
   V(harmony_top_level_await, "harmony top level await")
 
 #ifdef V8_INTL_SUPPORT
@@ -219,7 +218,8 @@ DEFINE_IMPLICATION(harmony_import_meta, harmony_dynamic_import)
 #endif
 
 // Features that are complete (but still behind --harmony/es-staging flag).
-#define HARMONY_STAGED_BASE(V)                                     \
+#define HARMONY_STAGED_BASE(V)                                    \
+  V(harmony_regexp_match_indices, "harmony regexp match indices") \
   V(harmony_private_methods, "harmony private methods in class literals")
 
 #ifdef V8_INTL_SUPPORT