* Add envoy metrics service protos

This patch imports protos from envoyproxy/data-plane-api and
prometheus/client_model to enable metrics service service feature in
SkyWalking OAP.
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Add Envoy related docs
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Update the LICENSE to include new protos license

From:
- envoyproxy/data-plane-api
- prometheus/client_model
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Add a complete config.yaml example
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Add note on Envoy dynamic config
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Add protoc-gen-validate license
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Add samples
Signed-off-by: NDhi Aurrahman <dio@tetrate.io>

* Make CI and license right.

* Update README.md

@dhi typo :P

* Update README.md

Another typo :P

* Delete metrics.json

metrics.json is included in identify.json and not be linked in document.

* Update and rename Spring-bean-plugins.md to Spring-annotation-plugin.md

* Update README.md

* Update README.md

[Performance Improvement]Backend streaming thread model improvement

* Zookeeper plugin

* Support to register different host/port at cluster coordinator. Only for Zookeeper and Consul

* Provide document for internalComHost and internalComPort

* Reset port to default.

* Make sure all document images ref from our Apache website.

* Change the statement.

* Support lettuce plugin

* lettuce plugin bugfix

* lettuce plugin fix license issue

* lettuce plugin fix cluster and config issue

* plugin lettuce compatible with low 5.0.x version

* lettuce plugin support version accurately describes on Supported-list.md

* plugin lettuce compatible with low 5.0.2 version

* lettuce plugin fix wrong batch method intercept point

* move lettuce to optional plugins

* fix ci issue

* fix ci issue

* Modify the description file

* Pom code optimization

* Optimization operation name

* Optimization operation name2

* fix gRPCHost

* fix gRPCHost

correct spelling error.

* Update trace-mode-grafana.json

Update heatmap expression

* Update trace-mode-grafana.json

* Update mesh-mode-grafana.json

fix bugs for more than one instance

* Update mesh-mode-grafana.json

Fix heatmap

* 🎉 PHP agent

* Update powered-by.md

Change user list order

* plugin support redisson

* Change a label name for  sw instance to avoid confict.

* Fix a wrong metric name.

* Fix too many counter instances.

* Set uptime to second.

* Fix format.

* Fix format

* Remove two unnecessary counter.

* Provide grafana dashboard settings and remove unnecessary metric.

* Provide a simple UI brief doc. Fix #2137

* Finish the basic codes of telemetry.

* Add many telemetry in oap.

* Fix a test case.

* Finish all telemetry metric.

* Fix format.

* Make telemetry works.

* Support JVM metrics.

* Add doc for telemetry.

* Fix typo.

* Fix #2135

* Support Gson plugin

* Update README.md

* Update README.md

* Provide consul cluster plugin.

* Change log and application config file.

* Add consul's config item into the docker's application.yml.

* Fixed bug.

* Add consul description into  readme.

* Add okhttp component license.

* Support webflux and spring mvc 5 plugin

* Change instrumentation

* Change instrumentation

* fix check style

* Add support 2.1.x instrumentation

2. Zookeeper implementation of the cluster module using name space to support using same zookeeper cluster by different OAP clusters.

* Support alarm in service instance and endpoint.

* Fix alarm default settings and document.

* Fix wrong default setting

* Make service instance and endpoint scopes available in alarm core.

* Fix alarm bug.

* Update document and user wall.

* Change format.

* user wall updated.

* Fix typo

* Correct namespace description

* Support sampling trace at server side and keep metric right.

* Add a trace sampling document

* Fix wrong default value.

* Fix document issue.

* Fix assemble issue.

* Fix wrong settings and doc.

* add TiDB configuration description.

* add tested mysql client driver version

Also fixed several bugs in this merge.

Notice of the system time setting.

* feat:Active System.env Config In Both Collector And agent.config.
1、moving related codes into apm-util module.
2、update Setting-override.md about how to use.

* resolve docs.

* typo

* finish test case.

* Update README.md

* support set config from system.envs.

* Update new protocol

* Support new protocol at agent side.

* Fix test case.

* Make backend supports new trace protocol

* Fix tests.

* Make all new services available in gRPC.

* Fix bugs.

* Finish new document for v2 trace protocol.

* Fix wrong version requirement of zk

* Fix trace query bug.

* Find a client side dictionary bug.

* Fix register bugs.

* Fix break doc links.

* Change some codes to make zipkin receiver works, not done yet.

* @adriancole Zipkin receiver is coming back again.

* Fix document and fix for Zipkin receiver.

* Fix some bugs.

* Fix register bug.

* Fix transfer bug for new backend core.

Fix typo

* ZooKeeper Version Compatibility

* Update backend-cluster.md

Reorganize words. cc @peng-yongsheng

* Update application.yml

* Update application.yml