add polardb pool (#420)

* fix

* fix：nacos

* feat: fix config Exception

* feat: format config

* feat: format config

* fix：

* fix：

* fix：

* fix：

* add polardb pool

* fix：

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Co-authored-by: ccl <[email protected]>
Co-authored-by: lijicode <[email protected]>
Co-authored-by: liji <[email protected]>

Author: 3 people