Merge bitcoin/bitcoin#29012: fuzz: Avoid timeout in bitdeque

fad1903b8a fuzz: Avoid timeout in bitdeque (MarcoFalke)

Pull request description:

  Avoid timeouts such as https://github.com/bitcoin/bitcoin/issues/28812#issuecomment-1842914664

  This is done by:

  * Limiting the maximum number of iterations if the maximum size of the container is "large" (see the magic numbers in the code).
  * Check the equality only once. This should be fine, because if a crash were to happen in the equality check, but the crash doesn't happen if further iterations were run, the fuzz engine should eventually find the crash by truncating the fuzz input.

ACKs for top commit:
  sipa:
    utACK fad1903b8a
  dergoegge:
    utACK fad1903b8a
  brunoerg:
    crACK fad1903b8a

Tree-SHA512: d3d83acb3e736b8fcaf5d17ce225ac82a9f9a2efea048512d2fed594ba6c76c25bae72eb0fab3276d4db37baec0752e5367cecfb18161301b921fed09693045e

src/test/fuzz/bitdeque.cpp

@@ -53,21 +53,11 @@ FUZZ_TARGET(bitdeque, .init = InitRandData)
         --initlen;
     }
 
-    LIMITED_WHILE(provider.remaining_bytes() > 0, 900)
+    const auto iter_limit{maxlen > 6000 ? 90U : 900U};
+    LIMITED_WHILE(provider.remaining_bytes() > 0, iter_limit)
     {
-        {
-            assert(deq.size() == bitdeq.size());
-            auto it = deq.begin();
-            auto bitit = bitdeq.begin();
-            auto itend = deq.end();
-            while (it != itend) {
-                assert(*it == *bitit);
-                ++it;
-                ++bitit;
-            }
-        }
-
-        CallOneOf(provider,
+        CallOneOf(
+            provider,
             [&] {
                 // constructor()
                 deq = std::deque<bool>{};
@@ -535,7 +525,17 @@ FUZZ_TARGET(bitdeque, .init = InitRandData)
                     assert(it == deq.begin() + before);
                     assert(bitit == bitdeq.begin() + before);
                 }
-            }
-        );
+            });
+    }
+    {
+        assert(deq.size() == bitdeq.size());
+        auto it = deq.begin();
+        auto bitit = bitdeq.begin();
+        auto itend = deq.end();
+        while (it != itend) {
+            assert(*it == *bitit);
+            ++it;
+            ++bitit;
+        }
     }
 }