Polish doc, remove old OAL description. (#3643)

* Polish doc, remove old OAL description.

* Add a new use case.

docs/en/guides/Java-Plugin-Development-Guide.md

@@ -365,7 +365,7 @@ Please follow there steps:
 1. Create sub modules under `apm-sniffer/apm-sdk-plugin` or `apm-sniffer/optional-plugins`, and the name should include supported library name and versions
 1. Follow this guide to develop. Make sure comments and test cases are provided.
 1. Develop and test.
+1. Provide the automatic test cases. Read existing cases in `test/plugin/scenarios`, and add your new one.
 1. Send the pull request and ask for review. 
-1. Provide the automatic test cases. 
-1. The plugin committers approve your plugins after automatic test cases provided and the tests passed in our CI.
+1. The plugin committers approve your plugins, plugin CI-with-IT, e2e and plugin tests passed.
 1. The plugin accepted by SkyWalking. 

docs/en/guides/backend-oal-scripts.md

 # Official OAL script
 First, read [OAL introduction](../concepts-and-designs/oal.md).
 
-Here is the official scrips is the `generated-analysis-x.y.z.jar/official_analysis.oal` file in distribution,
-also the [official_analysis.oal](../../../oap-server/generated-analysis/src/main/resources/official_analysis.oal) in source code repository.
+Find OAL script at the `/config/official_analysis.oal` of SkyWalking dist, since 6.3.
+You could change it(such as adding filter condition, or add new metrics) and reboot the OAP server, then it will affect.
 
-**Notice**, this file doesn't effect anything in runtime, although included in distribution.
-You need to use OAL tool code generator to build the real analysis codes from it.
-All generated codes are under `oal` folder in **oap-server/generated-analysis/target/generated-sources**.
+All metrics named in this script could be used in alarm and UI query. 
 
-All metrics named in this script could be used in alarm and UI query. Of course, you can change this 
-scripts and re-generate the analysis process and metrics, such as adding filter condition. 
+Notice,
 
 If you try to add or remove some metrics, UI may break, we only recommend you to do this when you plan
 to build your own UI based on the customization analysis core. 
\ No newline at end of file

docs/powered-by.md

@@ -103,7 +103,7 @@ or providing commercial products including Apache SkyWalking.
 1. Youzan.com 杭州有赞科技有限公司 http://www.youzan.com/
 1. zjs.com.cn 北京宅急送快运股份有限公司 http://www.zjs.com.cn/
 
-# User Cases
+# Use Cases
 ## Alibaba Cloud
 Support SkyWalking agents and formats in Tracing Analysis cloud service.
 
@@ -120,6 +120,12 @@ Deploy SkyWalking in production environments.
 
 Support 60+ Instances, Over 300k Calls Per Minute, Over 50k Spans Per Second
 
+## guazi.com
+Guazi.com uses SkyWalking monitoring 270+ services, 
+including topology + metrics analysis, and collecting 1.1+ billion traces per day with 100% sampling. 
+
+Plan is 1k+ services and 5 billion traces per day.
+
 ## Oscart
 Use multiple language agents from SkyWalking and its ecosystem, including SkyWalking Javaagent and [SkyAPM nodejs agent](https://github.com/SkyAPM/SkyAPM-nodejs). SkyWalking OAP platform acts as backend and visualization.