Add cluster etcd config to cluster.md.

* set Override is not working.

* Submodule update

* Add header.

* Check license header strictly

* Ignore header template

* Include more files to check list

* Refactor open edge.

* Make refactor works.

* Revert log back.

* Remove unnecessary codes.

* Open edge for all internal binding interceptors.

* Add document about JDK 9+ module.

* Change bytebuddy to 1.10.1(unreleased)

* Change document

* 1. Adopt the latest bytebudy changes(snapshot only), commit https://github.com/raphw/byte-buddy/commit/b60971156403ed8fba6124b8e424f0749917594a.
2. Remove disruptor by ArrayBlockingQueue, because Disruptor can't work in both JDK 8(1) and 9-12, if we don't add `--add-modules jdk.unsupported`
3. Doc update.

* Update README.md

* update gateway

* Add pattern logger to replace the easy logger.
* Doc update
* Support console log 

change `agent.span_limit_per_segment` default value to match the default value of `SPAN_LIMIT_PER_SEGMENT` in https://github.com/apache/skywalking/blob/master/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/conf/Config.java

* webflux

* Support undertow routing handler

* improve auto connect

* add config

* use int instread of atomic

* update format

* update doc

* update var name and doc

* fix

* Unified http status code usage

* fmt

* support elasticsearch address configuration with http scheme.

* update logical.

* Modify the thread pool of grpc server.

* add license header

* make param confingable

* Add sharing and Jaeger config.

* Remove grpc thread config from yml

* Remove the meta file

* Add dependency licenses check 

* Update backend-storage.md

* Update backend-storage.md

* Update ES-Server-FAQ.md

* improve AsyncSpan API: make #asyncFinish and #prepareForAsync can not invoke more than once
make the API more strong: make the plugin code bug fail-fast

* [maven-release-plugin] prepare release v6.3.0

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

* GC time metrics should be total time.

* Add it to change log.

* FYI @hanamily you missed to change this in self observability.

* fix changes.md typo

* fix typo

* Add changelog for 6.3.0 release.

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

* Update CHANGES.md

The current latency of the test service is too slow, causing it's not counted and
the query result is 0, this patch increases the latency intentionally by sleeping
1 second

* 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