[compiler] Enable --concurrent-inlining by default

As per the release plan in crbug.com/v8/12142.

Bug: v8:7790,v8:12142
Change-Id: I80e2a3c571681a968ea245d52adfa539e0e7ab7b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3127711
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76560}

src/flags/flag-definitions.h

@@ -711,7 +711,7 @@ DEFINE_INT(concurrent_recompilation_queue_length, 8,
            "the length of the concurrent compilation queue")
 DEFINE_INT(concurrent_recompilation_delay, 0,
            "artificial compilation delay in ms")
-DEFINE_BOOL(concurrent_inlining, false,
+DEFINE_BOOL(concurrent_inlining, true,
             "run optimizing compiler's inlining phase on a separate thread")
 DEFINE_BOOL(stress_concurrent_inlining, false,
             "makes concurrent inlining more likely to trigger in tests")