[ISSUE #3680] Add shenyu-client-http-springmvc unit test

[847850277]

Hi, community
I have finished unit test "shenyu-client-http-springmvc".
see Issues #3680
please review code.

Make sure that:

• You have read the contribution guidelines.
• You submit test cases (unit or integration tests) that back your changes.
• Your local test passed ./mvnw clean install -Dmaven.javadoc.skip=true.

[codecov-commenter]

Codecov Report

Merging #3681 (9cbdf6c) into master (59e7a95) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #3681      +/-   ##
============================================
- Coverage     62.96%   62.83%   -0.13%     
- Complexity     5878     5889      +11     
============================================
  Files           902      904       +2     
  Lines         24609    24743     +134     
  Branches       2229     2252      +23     
============================================
+ Hits          15494    15547      +53     
- Misses         7715     7789      +74     
- Partials       1400     1407       +7     

Impacted Files	Coverage Δ
...client/springmvc/init/ContextRegisterListener.java	0.00% <0.00%> (ø)
...t/springmvc/init/SpringMvcClientEventListener.java	59.55% <0.00%> (ø)

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[loongs-zhang]

I will review it later.

[loongs-zhang]

@847850277 have fun with contribution !