【doc】add auto test doc

[justforstudy-A]

What type of PR is this?

/feat

Which issue(s) this PR fixes:

Fixes #974

Use case description:

1. add doc for auto test
2. add integration test dir for auto test
3. add upper for context num for flowcontrol

Does this PR introduce a user-facing change?

No

Additional documentation e.g., usage docs, etc.:

No

[codecov]

Codecov Report

Base: 44.50% // Head: 44.34% // Decreases project coverage by -0.15% ⚠️

Coverage data is based on head (dd0c4e1) compared to base (6133b39).
Patch has no changes to coverable lines.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #973      +/-   ##
=============================================
- Coverage      44.50%   44.34%   -0.16%     
+ Complexity      2805     2797       -8     
=============================================
  Files            660      660              
  Lines          14580    14580              
  Branches        1620     1620              
=============================================
- Hits            6489     6466      -23     
- Misses          7314     7337      +23     
  Partials         777      777              

Flag	Coverage Δ
unittests	44.34% <ø> (-0.16%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...i/fowcontrol/res4j/chain/context/ChainContext.java	91.66% <ø> (+4.16%)	⬆️
...er/spring/interceptor/RouteHandlerInterceptor.java	0.00% <0.00%> (-80.96%)	⬇️
...nterceptors/DiscoveryClientServiceInterceptor.java	38.46% <0.00%> (-30.77%)	⬇️
...router/dubbo/strategy/type/ObjectTypeStrategy.java	71.42% <0.00%> (-14.29%)	⬇️
...mplement/service/tracing/sender/TracingSender.java	63.49% <0.00%> (-4.77%)	⬇️
...ter/spring/interceptor/FeignClientInterceptor.java	75.00% <0.00%> (-3.13%)	⬇️
...y/interceptors/health/EurekaHealthInterceptor.java	64.70% <0.00%> (+5.88%)	⬆️
...r/spring/interceptor/HystrixActionInterceptor.java	66.66% <0.00%> (+11.11%)	⬆️
...awei/registry/handler/SingleStateCloseHandler.java	89.28% <0.00%> (+17.85%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[robotLJW]

/lgtm