[maglev] Fix test flake due to racing the compiler thread

Bump the limit to give TF enough time to finish compiling. The
`keep_going` limit is fairly ugly, but it lets us test the real
(=concurrent) pipeline.

Bug: v8:7700
Fixed: v8:13176
Change-Id: Iba97111d752c8a4894e99ab57e8f42abcc8c29bb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3862204
Auto-Submit: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82778}

test/mjsunit/maglev/tier-to-ml-to-tf.js

@@ -13,7 +13,7 @@ function f(x) {
   return y;
 }
 
-let keep_going = 100000;  // A counter to avoid test hangs on failure.
+let keep_going = 10000000;  // A counter to avoid test hangs on failure.
 
 function g() {
   // Test that normal tiering (without OptimizeFooOnNextCall) works.