feat:support polaris server nearby backup LB.

[fuyuwei01]

PR Type

Describe what this PR does for and how you did.

Adding the issue link (#xxx) if possible.

Note

Checklist

• Add information of this PR to CHANGELOG.md in root of project.
• Add documentation in javadoc or comment below the PR if necessary.

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.13%. Comparing base (02e0ae6) to head (fec5083).
Report is 1 commits behind head on 2021.

Files with missing lines	Patch %	Lines
...laris/context/config/PolarisContextProperties.java	50.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               2021    #1629   +/-   ##
=========================================
  Coverage     67.13%   67.13%           
  Complexity       20       20           
=========================================
  Files           340      340           
  Lines          8310     8323   +13     
  Branches       1028     1028           
=========================================
+ Hits           5579     5588    +9     
- Misses         2244     2248    +4     
  Partials        487      487           

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[SkyeBeFreeman]

LGTM.