RFR: New script: find hot files/ sort by last_mod date

[Yi Yang]

Hi, I'm surprised there is such an interesting project in OpenJDK. I've also written an interesting script and want to contribute to friday-stats. It could:

1. Find hot files which have many commit messages, output looks like:
269   2021-04-14      src/hotspot/share/gc/g1/g1CollectedHeap.cpp                                             
217   2021-03-30      src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp                                      
134   2021-04-12      src/hotspot/share/gc/g1/g1CollectedHeap.hpp                                             
127   2021-04-06      src/hotspot/share/gc/g1/g1ConcurrentMark.cpp                                            
99    2021-04-14      src/hotspot/share/gc/shared/genCollectedHeap.cpp                                        
95    2021-04-15      src/hotspot/share/gc/parallel/psParallelCompact.cpp                                     
...
2. Sort files by last commit date, output looks like:
17    2021-04-15      src/hotspot/share/services/diagnosticCommand.hpp                                        
64    2021-04-15      src/hotspot/share/prims/jvmtiExport.cpp                                                 
79    2021-04-15      src/hotspot/share/classfile/classLoader.cpp                                             
16    2021-04-15      src/hotspot/share/gc/g1/g1FullGCPrepareTask.cpp                                         
17    2021-04-15      src/hotspot/share/gc/g1/g1FullGCMarker.inline.hpp                                       
19    2021-04-15      src/hotspot/share/jvmci/compilerRuntime.cpp                                             
...

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Commit messages:
 - New script: find hot files/ sort by last_mod date

Changes: https://git.openjdk.java.net/friday-stats/pull/2/files
 Webrev: https://webrevs.openjdk.java.net/?repo=friday-stats&pr=2&range=00
  Stats: 138 lines in 1 file changed: 138 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/friday-stats/pull/2.diff
  Fetch: git fetch https://git.openjdk.java.net/friday-stats pull/2/head:pull/2

PR: https://git.openjdk.java.net/friday-stats/pull/2