rename heap_trace.txt to gc.log and make gc log rotatable

[nobodyiam]

No description provided.

[codecov-io]

Codecov Report

Merging #1526 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1526      +/-   ##
============================================
- Coverage      48.7%   48.68%   -0.02%     
+ Complexity     1885     1884       -1     
============================================
  Files           394      394              
  Lines         11429    11429              
  Branches       1174     1174              
============================================
- Hits           5566     5564       -2     
- Misses         5438     5439       +1     
- Partials        425      426       +1

Impacted Files	Coverage Δ	Complexity Δ
.../apollo/internals/RemoteConfigLongPollService.java	76.68% <0%> (-1.23%)	27% <0%> (-1%)

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[coveralls]

Coverage decreased (-0.009%) to 52.411% when pulling 54783a9 on nobodyiam:rotate-gc-log into a8369f8 on ctripcorp:master.