Merge bitcoin/bitcoin#28178: fuzz: Generate with random libFuzzer settings

fa3a410 fuzz: Set -rss_limit_mb=8000 for generate as well (MarcoFalke)
fa4e396 fuzz: Generate with random libFuzzer settings (MarcoFalke)

Pull request description:

  Sometimes a libFuzzer setting like `-use_value_profile=1` helps [0], sometimes it hurts [1].

  [0] bitcoin/bitcoin#20789 (comment)
  [1] bitcoin/bitcoin#27888 (comment)

  By picking a random value, it is ensured that at least some of the runs will have the beneficial configuration set.

  Also, set `-max_total_time` to prevent slow fuzz targets from getting a larger time share, or possibly peg to a single core for a long time and block the python script from exiting for a long time. This can be improved in the future. For example, the python script can exit after some time (bitcoin/bitcoin#20752 (comment)). Alternatively, it can measure if coverage progress was made and run for less time if no progress has been made recently anyway, so that more time can be spent on targets that are new or still make progress.

ACKs for top commit:
  murchandamus:
    utACK fa3a410
  dergoegge:
    utACK fa3a410
  brunoerg:
    light ACK fa3a410

Tree-SHA512: bfd04a76ca09aec612397bae5f3f263a608faa7087697169bd4c506c8195c4d2dd84ddc7fcd3ebbc75771eab618fad840af819114968ca3668fc730092376768

Author: fanquake

test/fuzz/test_runner.py

@@ -11,6 +11,7 @@
 import configparser
 import logging
 import os
+import random
 import subprocess
 import sys
 
@@ -264,9 +265,13 @@ def job(command, t, t_env):
     for target, t_env in targets:
         target_corpus_dir = corpus_dir / target
         os.makedirs(target_corpus_dir, exist_ok=True)
+        use_value_profile = int(random.random() < .3)
         command = [
             os.path.join(build_dir, 'src', 'test', 'fuzz', 'fuzz'),
-            "-runs=100000",
+            "-rss_limit_mb=8000",
+            "-max_total_time=6000",
+            "-reload=0",
+            f"-use_value_profile={use_value_profile}",
             target_corpus_dir,
         ]
         futures.append(fuzz_pool.submit(job, command, target, t_env))