[#11729] Update agent's realipheader value to the list type.

[jaehong-kim]

11729

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 20 lines in your changes missing coverage. Please review.

Project coverage is 36.89%. Comparing base (e184ef3) to head (7fac070). Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
...trap/plugin/request/util/RealIpHeaderResolver.java	0.00%	20 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #11742 +/- ## ========================================= Coverage 36.89% 36.89% + Complexity 12400 12398 -2 ========================================= Files 4104 4104 Lines 100673 100680 +7 Branches 10542 10542 ========================================= + Hits 37145 37148 +3 - Misses 60534 60536 +2 - Partials 2994 2996 +2 ```

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