[future] Use mid-tier regalloc for huge functions

Stage the --turbo-use-mid-tier-regalloc-for-huge-functions behind
--future.

R=thibaudm@chromium.org

Bug: v8:12287, v8:12320
Change-Id: I7145ca1b022bfdcb0b61d6666daf855f14cbc4ce
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3236547Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77549}

src/flags/flag-definitions.h

@@ -923,8 +923,8 @@ DEFINE_BOOL(turbo_compress_translation_arrays, false,
             "compress translation arrays (experimental)")
 DEFINE_BOOL(turbo_inline_js_wasm_calls, true, "inline JS->Wasm calls")
 DEFINE_BOOL(turbo_use_mid_tier_regalloc_for_huge_functions, false,
-            "fall back to the mid-tier register allocator for huge functions "
-            "(experimental)")
+            "fall back to the mid-tier register allocator for huge functions")
+DEFINE_WEAK_IMPLICATION(future, turbo_use_mid_tier_regalloc_for_huge_functions)
 DEFINE_BOOL(turbo_force_mid_tier_regalloc, false,
             "always use the mid-tier register allocator (for testing)")