generic#invoke (go to java)

[pantianying]

What this PR does:
add generic#invoke (go to java)
Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
还缺少一个filter，处理请求参数中有struct的情况。我下周会增加

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #122 into develop will increase coverage by 0.74%.
The diff coverage is 48.1%.

@@             Coverage Diff             @@
##           develop     #122      +/-   ##
===========================================
+ Coverage    67.73%   68.48%   +0.74%     
===========================================
  Files           69       71       +2     
  Lines         4383     4461      +78     
===========================================
+ Hits          2969     3055      +86     
+ Misses        1119     1106      -13     
- Partials       295      300       +5

Impacted Files	Coverage Δ
config/generic_service.go	0% <0%> (ø)
config/config_loader.go	53.73% <0%> (-2.52%)	⬇️
config/reference_config.go	82.55% <25%> (-9.45%)	⬇️
filter/impl/generic_filter.go	58.33% <58.33%> (ø)
cluster/cluster_impl/base_cluster_invoker.go	48.93% <0%> (-19.15%)	⬇️
protocol/dubbo/readwriter.go	74.35% <0%> (+2.56%)	⬆️
config_center/zookeeper/listener.go	86.95% <0%> (+4.34%)	⬆️
protocol/dubbo/codec.go	82.35% <0%> (+8.82%)	⬆️
... and 2 more

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