Fix 2.6.x LoadBalance SPI not work

[wegod]

What is the purpose of the change

fix bug see #11644

Brief changelog

Add compatible method of com.alibaba.dubbo.rpc.Result and com.alibaba.dubbo.rpc.Invoker

Verifying this change

I test calling 2.6.x's method both sync and async

Checklist

• Make sure there is a GitHub_issue field for the change (usually before you start working on it). Trivial changes like typos do not require a GitHub issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Check if is necessary to patch to Dubbo 3 if you are work on Dubbo 2.7
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Add some description to dubbo-website project if you are requesting to add a feature.
• GitHub Actions works fine on your own branch.
• If this contribution is large, please follow the Software Donation Guide.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication

[codecov-commenter]

Codecov Report

Merging #11730 (a4ff87c) into 3.1 (16c61c5) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##                3.1   #11730      +/-   ##
============================================
- Coverage     64.74%   64.70%   -0.04%     
  Complexity       14       14              
============================================
  Files          1431     1431              
  Lines         60034    60036       +2     
  Branches       8827     8827              
============================================
- Hits          38867    38848      -19     
- Misses        17100    17114      +14     
- Partials       4067     4074       +7     

Impacted Files	Coverage Δ
...e/src/main/java/com/alibaba/dubbo/rpc/Invoker.java	0.00% <0.00%> (ø)
...le/src/main/java/com/alibaba/dubbo/rpc/Result.java	10.25% <0.00%> (-0.27%)	⬇️

... and 13 files with indirect coverage changes

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