feat: support hash key option in loadbalance

[welkeyever]

What type of PR is this?

feat

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• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

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feat: 在负载均衡中支持 hashkey 选项

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en: Add support for custom hash key configuration in load balancing. Users can now specify a custom hash key option when using consistent hash load balancing algorithm, providing more flexibility for routing decisions based on specific request parameters.
zh(optional):

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[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.32%. Comparing base (8240939) to head (b500f6d).

Files with missing lines	Patch %	Lines
pkg/app/client/loadbalance/lbcache.go	50.00%	1 Missing and 1 partial ⚠️
pkg/app/client/loadbalance/loadbalance.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1471      +/-   ##
==========================================
- Coverage   86.37%   86.32%   -0.05%     
==========================================
  Files         149      149              
  Lines       14429    14433       +4     
==========================================
- Hits        12463    12460       -3     
- Misses       1428     1430       +2     
- Partials      538      543       +5     

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