Fix data race bug: In concurrency scenario, RegisterRuleCheckSlotForResource and Entry will compete the slots in SlotChain

[louyuting]

Describe what this PR does / why we need it

Does this pull request fix one issue?

"Fixes #335 "
"Fixes #336 "

Describe how you did it

Describe how to verify it

run unit test

Special notes for reviews

[codecov-io]

Codecov Report

Merging #337 (811cacc) into master (365844b) will increase coverage by 0.07%.
The diff coverage is 48.14%.

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
+ Coverage   50.75%   50.83%   +0.07%     
==========================================
  Files          69       69              
  Lines        3822     3842      +20     
==========================================
+ Hits         1940     1953      +13     
- Misses       1614     1621       +7     
  Partials      268      268              

Impacted Files	Coverage Δ
core/system/rule_manager.go	80.39% <ø> (-0.38%)	⬇️
core/misc/resource_slot_chain.go	37.68% <36.36%> (-0.06%)	⬇️
core/base/slot_chain.go	97.82% <100.00%> (+0.12%)	⬆️
core/system/slot.go	49.15% <0.00%> (-1.70%)	⬇️
core/hotspot/slot.go	27.77% <0.00%> (+2.77%)	⬆️
core/flow/slot.go	46.66% <0.00%> (+3.33%)	⬆️
core/isolation/slot.go	7.69% <0.00%> (+3.84%)	⬆️
core/circuitbreaker/slot.go	100.00% <0.00%> (+5.55%)	⬆️

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[luckyxiaoqiang]

LGTM

[binbin0325]

LGTM.

[binbin0325]

LGTM