Allow negative paramIndex in ParamFlowRule

[CarpenterLee]

Signed-off-by: Carpenter Lee hooleeucas@163.com

Describe what this PR does / why we need it

Negative paramIndex in ParamFlowRule is useful in some case, eg when we want to count params from the opposite direction. But Sentinel does not allow negative paramIndex in ParamFlowRule now.

Does this pull request fix one issue?

NONE

Describe how you did it

Change ParamFlowRuleUtil and ParamFlowChecker to allow negative paramIndex in ParamFlowRule

Describe how to verify it

Run unit test cases

Special notes for reviews

[codecov-io]

Codecov Report

Merging #549 into master will increase coverage by 0.51%.
The diff coverage is 55.55%.

@@             Coverage Diff              @@
##             master     #549      +/-   ##
============================================
+ Coverage     37.51%   38.02%   +0.51%     
- Complexity     1102     1112      +10     
============================================
  Files           259      259              
  Lines          8171     8177       +6     
  Branches       1113     1115       +2     
============================================
+ Hits           3065     3109      +44     
+ Misses         4715     4664      -51     
- Partials        391      404      +13

Impacted Files	Coverage Δ	Complexity Δ
...inel/slots/block/flow/param/ParamFlowRuleUtil.java	53.7% <0%> (ø)	20 <0> (-1)	⬇️
...tinel/slots/block/flow/param/ParamFlowChecker.java	46.98% <62.5%> (+0.23%)	20 <1> (+1)	⬆️
...l/cluster/server/connection/ConnectionManager.java	74% <0%> (-2%)	10% <0%> (-1%)
...a/com/alibaba/csp/sentinel/node/StatisticNode.java	81.96% <0%> (-1.64%)	28% <0%> (-1%)
...a/csp/sentinel/slots/statistic/base/LeapArray.java	69.62% <0%> (+3.79%)	25% <0%> (+1%)	⬆️
...a/csp/sentinel/slots/statistic/base/LongAdder.java	31.91% <0%> (+14.89%)	10% <0%> (+6%)	⬆️
...a/csp/sentinel/slots/statistic/base/Striped64.java	60.41% <0%> (+34.37%)	10% <0%> (+5%)	⬆️

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[sczyh30]

LGTM

[sczyh30]

Thanks!