Revert "[heap] Disable map space with --future"

This reverts commit 74c68e2a.

Reason for revert: https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20UBSan/21353/overview

Original change's description:
> [heap] Disable map space with --future
>
> Original CL got reverted, this time the failing test should be fixed.
>
> Bug: v8:12578
> Change-Id: Id2d8801f07742e8b00884fefec8200e4270f4250
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3657434
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#80668}

Bug: v8:12578
Change-Id: I2ee20c79ec09ff4f7bece6ddcc1c3a5cd9351223
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3647692
Owners-Override: Tobias Tebbi <tebbi@chromium.org>
Auto-Submit: Tobias Tebbi <tebbi@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#80669}

src/flags/flag-definitions.h

@@ -532,7 +532,7 @@ DEFINE_WEAK_IMPLICATION(future, flush_baseline_code)
 DEFINE_WEAK_IMPLICATION(future, short_builtin_calls)
 #endif
 DEFINE_WEAK_NEG_IMPLICATION(future, write_protect_code_memory)
-DEFINE_WEAK_NEG_IMPLICATION(future, use_map_space)
+DEFINE_WEAK_IMPLICATION(future, compact_maps)
 
 DEFINE_BOOL_READONLY(dict_property_const_tracking,
                      V8_DICT_PROPERTY_CONST_TRACKING_BOOL,

test/unittests/api/isolate-unittest.cc

@@ -144,11 +144,7 @@ void CrashKeyCallback(v8::CrashKeyId id, const std::string& value) {
 }  // namespace
 TEST_F(IsolateTest, SetAddCrashKeyCallback) {
   isolate()->SetAddCrashKeyCallback(CrashKeyCallback);
-
-  internal::Isolate* i_isolate =
-      reinterpret_cast<internal::Isolate*>(isolate());
-  const bool has_map_space = i_isolate->heap()->map_space() != nullptr;
-  EXPECT_EQ(crash_keys.size(), has_map_space ? 6u : 5u);
+  EXPECT_EQ(crash_keys.size(), 6u);
 }
 
 }  // namespace v8