add generic parameter for RowLock

[javeme]

Change-Id: I309b89846ca15d58ea39095d406a0b0b5de510e7

[codecov]

Codecov Report

Merging #42 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master      #42      +/-   ##
============================================
+ Coverage        78%   78.08%   +0.07%     
- Complexity      584      585       +1     
============================================
  Files            55       55              
  Lines          1869     1871       +2     
  Branches        275      275              
============================================
+ Hits           1458     1461       +3     
  Misses          286      286              
+ Partials        125      124       -1

Impacted Files	Coverage Δ	Complexity Δ
...java/com/baidu/hugegraph/concurrent/LockGroup.java	96% <100%> (+0.34%)	13 <0> (ø)	⬇️
.../main/java/com/baidu/hugegraph/perf/Stopwatch.java	87.75% <0%> (+2.04%)	21% <0%> (+1%)	⬆️

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