Merge #19052: tests: Don't limit fuzzing inputs to 1 MB for afl-fuzz (now: ∞ ∀ fuzzers)

6a239e72eb tests: Don't limit fuzzing inputs to 1 MB for afl-fuzz (now: ∞ ∀ fuzzers) (practicalswift)

Pull request description:

  Don't limit fuzzing inputs to 1 MB for `afl-fuzz`.

  This change provides a level playing field for all fuzzers which allows for fair benchmarking using projects such as the excellent [FuzzBench](https://github.com/google/fuzzbench) project.

  Prior to this commit we limited `afl-fuzz` to ≤1 MB inputs but allowed unlimited length inputs for all other fuzzers.

ACKs for top commit:
  MarcoFalke:
    ACK 6a239e72eb The maximum data size should be a runtime option, not a compile time hardcoded value.

Tree-SHA512: dad176ae39aa09fe919e057008ab0670b9da72909bfeb8f0e8b9ae93b65514f2e25a1d51be89a32be9122fc412edf49234dfd9a44beb974b25fda387fd7bf174

src/test/fuzz/fuzz.cpp

@@ -19,8 +19,6 @@ static bool read_stdin(std::vector<uint8_t>& data)
     ssize_t length = 0;
     while ((length = read(STDIN_FILENO, buffer, 1024)) > 0) {
         data.insert(data.end(), buffer, buffer + length);
-
-        if (data.size() > (1 << 20)) return false;
     }
     return length == 0;
 }