refact: params improve for personal rank api

[imbajin]

tiny params improve, will update the ppr doc later (the max_diff will implement in future)

[codecov]

Codecov Report

Merging #1695 (62acaaa) into master (b1cec5a) will decrease coverage by 0.36%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##             master    #1695      +/-   ##
============================================
- Coverage     67.14%   66.78%   -0.37%     
+ Complexity     7084     7061      -23     
============================================
  Files           420      420              
  Lines         34684    34689       +5     
  Branches       4810     4811       +1     
============================================
- Hits          23290    23166     -124     
- Misses         9057     9186     +129     
  Partials       2337     2337              

Impacted Files	Coverage Δ
...baidu/hugegraph/api/traversers/CrosspointsAPI.java	100.00% <ø> (ø)
...aidu/hugegraph/api/traversers/PersonalRankAPI.java	70.73% <33.33%> (+1.28%)	⬆️
...egraph/backend/store/mysql/MysqlStoreProvider.java	33.33% <0.00%> (-66.67%)	⬇️
...aidu/hugegraph/backend/store/mysql/MysqlStore.java	63.95% <0.00%> (-17.77%)	⬇️
...idu/hugegraph/backend/store/mysql/MysqlTables.java	76.51% <0.00%> (-13.17%)	⬇️
...u/hugegraph/backend/store/mysql/MysqlSessions.java	57.89% <0.00%> (-10.53%)	⬇️
...aidu/hugegraph/backend/store/mysql/MysqlTable.java	75.82% <0.00%> (-5.77%)	⬇️
...baidu/hugegraph/backend/store/mysql/MysqlUtil.java	93.22% <0.00%> (-3.39%)	⬇️
...va/com/baidu/hugegraph/task/ServerInfoManager.java	71.34% <0.00%> (-2.81%)	⬇️
...ain/java/com/baidu/hugegraph/task/TaskManager.java	69.06% <0.00%> (-1.44%)	⬇️
... and 3 more

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