* Add changelog for 6.3.0 release.

* Update CHANGES.md
Co-Authored-By: Nkezhenxu94 <kezhenxu94@apache.org>

* Update CHANGES.md

* Fixed java agent cannot trace gRPC stream service

* add http

* update plugin

* Add StaticMethodsAroundInterceptor to be injected.

* move to options plugin

* move folder

* update pom

* support https

* add witness class

* Make JDK9-11 available for bootstrap instrumentation

* Remove temp folder of old bootstrap instrumentation requirement.

* remove witness ,work for jdk6,7,8,9,10,11

* Make JDK 12 works.

* move jdk-http-plugin to bootstrap-plugins folder

* add httpsclient

* update README.md

* Support upgrade backend w/o rebooting agents

* Make JDK9-11 available for bootstrap instrumentation

* Remove temp folder of old bootstrap instrumentation requirement.

* Remove javassist dependency

*   Finish the PR.

* Change doc title level.

* Remove the duplicated codes.

* POC: Intercept successfully.

* Refactor codes

* Build the new core

* Setup the new core.

* Push the javassist version to 3.23.2-GA, as it is the last version supports JDK 1.6 compile, according to https://github.com/jboss-javassist/javassist/blob/rel_3_23_2_ga/pom.xml#L149-L160

* Finish the all codes.

* Document updated for bootstrap instrumentation.

* Add a notice to document.

* Remove unexpected file.

* Set javassist version right. Add judge in core interceptors

* Fixe no log bridge implementation

If transform throw exception, the stream observer won't call the onCompleted method, then the stream observer will wait it finish until the timeout. (#3163)

* servlet 2.5

* method exist

* update MethodUtil

* Update MethodUtil.java

Add a comment to the new core util method. @candyleer I am concerning this method will be used widely even unnecessary.

fixed for #3135:createEntrySpan should get SamplingService only if it required ( carrier is valid) (#3137)

* Fix 3096

* Make finish more stable in async APIs

* Change OAL generator tool to runtime.

Step 1. change project structure. API links and maven pom.

* Part of metrics class generation

* Metrcis class generated.

* Set up the basic structure of new OAL engine.

* Finish metrics generation.

* Support dispatcher generation.

* Format codes.

* Generate dispatcher all methods.

* Implement disable in hardcode.

* Clear up

* Fix compile startup.

* Update license and document of new OAL engine.

* Fix rat.

* Disable class output in default

* Copy from @kezhenxu94 's test PR, https://github.com/apache/skywalking/pull/3110

* Wait for the mount command to finish

* improve ContextManager.stopSpan and awaitFinishAsync performance: call ThreadLocal only once
For the [JMH benchmark test](https://gitlab.com/qxo1/Common-JMH-benchmark/-/jobs/251025992) :
On gitlab CI(java 8): call ThreadLocal once vs twice fast over 10%
My T480 java 8 : fast over 40%; java 11: fast over 50%;

[The JMH benchmark code ](https://github.com/qxo/Common-JMH-benchmark/blob/master/src/main/java/test/ThreadLocalGetXTimeBenchmark.java)

* Update apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/ContextManager.java
Co-Authored-By: Nkezhenxu94 <kezhenxu94@163.com>

* Update apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/ContextManager.java
Co-Authored-By: Nkezhenxu94 <kezhenxu94@163.com>

* Update apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/ContextManager.java
Co-Authored-By: 吴晟 Wu Sheng <wu.sheng@foxmail.com>

* Correct spelling errors in the network protocol.

* update protocol submodule commit id.

* Fix wrong logger name

* Fix more wrong logger names in agent side

* Set up 10 seconds deadline after gRPC client sending
 * The duration of deadline contains three segments: connecting,
   request and response

For blocking stub, I just set deadline before invoke service. For
bi-streaming stub, I found all of them are used as a blocking style,
that after getting streaming response client stub just close current
streaming. Base on above reality, I pick the same way as blocking one.

* spring_async_plugin

* fix

* fix

* fix

* fix

* format fix

* rename

* fix

* fix version

* Update SWCallable.java

* Update Supported-list.md

* Update Supported-list.md

* AsyncAppender

* improve performance

* fix mdc issue

* fix mdc

* add Async demo

* [maven-release-plugin] prepare release v6.2.0

* [maven-release-plugin] prepare for next development iteration

* Update UI.

* Fix CPU time again

* Update UI.

This reverts commit db8c4546.

* Support bootstrap class enhance and fix OOM by empty stack of exception.

* Agent document update

* Remove a word.

* Fix wrong cause exception search.

* Fix the condition

* Revert bootstrap class loader enhance.

* Remove import.

* no message

* Add config to control tracing sql parameters