Fix SimpleDateFormat concurrent issue in CspFormatter

[yikangfeng]

Describe what this PR does / why we need it

解决了 #547 我提的issue 存在的问题

Does this pull request fix one issue?

Fixes #547

Describe how you did it

将SimpleDateFormat 包装为ThreadLocal方式来解决多线程安全问题

Describe how to verify it

Special notes for reviews

[CLAassistant]

All committers have signed the CLA.

[sczyh30]

Hi, thanks for contributing. Could you please sign the CLA here? And please make sure the email of your commits match your GitHub email.

---

感谢贡献，请将 commit 对应的 email 调整成与 GitHub 的 email 相匹配并 确认一下 CLA。另外请 reformat 相关代码，确保符合 Alibaba Java Code Guideline。

[codecov-io]

Codecov Report

Merging #548 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #548      +/-   ##
============================================
- Coverage     37.96%   37.91%   -0.05%     
+ Complexity     1111     1108       -3     
============================================
  Files           259      259              
  Lines          8177     8173       -4     
  Branches       1115     1113       -2     
============================================
- Hits           3104     3099       -5     
- Misses         4668     4670       +2     
+ Partials        405      404       -1

Impacted Files	Coverage Δ	Complexity Δ
...ava/com/alibaba/csp/sentinel/log/CspFormatter.java	100% <100%> (ø)	4 <3> (ø)	⬇️
...a/csp/sentinel/slots/statistic/base/Striped64.java	56.25% <0%> (-4.17%)	8% <0%> (-2%)
...tinel/slots/block/flow/param/ParamFlowChecker.java	46.75% <0%> (-0.24%)	19% <0%> (-1%)

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[codecov-io]

Codecov Report

Merging #548 into master will increase coverage by 0.45%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #548      +/-   ##
============================================
+ Coverage     37.51%   37.96%   +0.45%     
- Complexity     1102     1110       +8     
============================================
  Files           259      259              
  Lines          8171     8173       +2     
  Branches       1113     1113              
============================================
+ Hits           3065     3103      +38     
+ Misses         4715     4666      -49     
- Partials        391      404      +13

Impacted Files	Coverage Δ	Complexity Δ
...ava/com/alibaba/csp/sentinel/log/CspFormatter.java	100% <100%> (ø)	4 <3> (ø)	⬇️
...s/block/flow/controller/RateLimiterController.java	79.31% <0%> (-10.35%)	7% <0%> (-1%)
...a/com/alibaba/csp/sentinel/node/StatisticNode.java	81.96% <0%> (-1.64%)	27% <0%> (-2%)
...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 for contributing!