[libFuzzer] Include TEMP_MAX_LEN in Fuzzer::PrintStats.

[kcc]

ouch. 10 is too magic.
I've seen hundreds of these printed in a row, i.e. 10 will be too small.
in other cases 10 will be to large.
I wonder if we want to print it as one more number in regular Fuzzer::PrintStats lines, e.g. "lim: 123", like here:
#3145 REDUCE cov: 6 ft: 7 corp: 5/9b lim: 123 exec/s: 0 rss: 37Mb

If so, we'll need to also update the docs to explain what that is.

I am not sure, there might be another better way.

[morehouse]

• Revert "[libFuzzer] Reduce frequency of TEMP_MAX_LEN prints."
• Print TEMP_MAX_LEN in Fuzzer::PrintStats.

[morehouse]

• Remove old TEMP_MAX_LEN print.

[kcc]

LGTM

compiler-rt/lib/fuzzer/FuzzerInternal.h

private:
   bool RunningCB = false;
 
   bool GracefulExitRequested = false;
 
   size_t TotalNumberOfRuns = 0;
   size_t NumberOfNewUnitsAdded = 0;
 
   size_t LastCorpusUpdateRun = 0;
+  size_t LastTmpMaxPrintRun = 0;
 
   bool HasMoreMallocsThanFrees = false;
   size_t NumberOfLeakDetectionAttempts = 0;
 
   system_clock::time_point LastAllocatorPurgeAttemptTime = system_clock::now();
 
   UserCallback CB;
   InputCorpus &Corpus;

compiler-rt/lib/fuzzer/FuzzerLoop.cpp

while (true) {
 
     // Update TmpMaxMutationLen
     if (Options.LenControl) {
       if (TmpMaxMutationLen < MaxMutationLen &&
           TotalNumberOfRuns - LastCorpusUpdateRun >
               Options.LenControl * Log(TmpMaxMutationLen)) {
         TmpMaxMutationLen =
             Min(MaxMutationLen, TmpMaxMutationLen + Log(TmpMaxMutationLen));
-        if (TmpMaxMutationLen <= MaxMutationLen)
+        if (TmpMaxMutationLen <= MaxMutationLen &&
+            TotalNumberOfRuns - LastTmpMaxPrintRun >
+                Options.LenControl * Log(TmpMaxMutationLen) * 10) {
           Printf("#%zd\tTEMP_MAX_LEN: %zd (%zd %zd)\n", TotalNumberOfRuns,
                  TmpMaxMutationLen, Options.LenControl,
                  LastCorpusUpdateRun);
+          LastTmpMaxPrintRun = TotalNumberOfRuns;
+        }
         LastCorpusUpdateRun = TotalNumberOfRuns;
       }
     } else {
       TmpMaxMutationLen = MaxMutationLen;
     }
 
     // Perform several mutations and runs.
     MutateAndTestOne();