Add changelog for 6.1

[wu-sheng]

Because we were preparing graduation, 6.1 comes a little late :) But we are very close to it. Here is a very long changelog for SkyWalking 6.1, and no incubating anymore.

6.1.0

Project

SkyWalking graduated as Apache Top Level Project.

• Support compiling project agent, backend, UI separately.

Java Agent

• Support Vert.x Core 3.x plugin.
• Support Apache Dubbo plugin.
• Support use_qualified_name_as_endpoint_name and use_qualified_name_as_operation_name configs in SpringMVC plugin.
• Support span async close APIs in core. Used in Vert.x plugin.
• Support MySQL 5,8 plugins.
• Support set instance id manually(optional).
• Support customize enhance trace plugin in optional list.
• Support to set peer in Entry Span.
• Support Zookeeper plugin.
• Fix Webflux plugin created unexpected Entry Span.
• Fix Kafka plugin NPE in Kafka 1.1+
• Fix wrong operation name in postgre 8.x plugin.
• Fix RabbitMQ plugin NPE.
• Fix agent can't run in JVM 6/7, remove module-info.class.
• Fix agent can't work well, if there is whitespace in agent path.
• Fix Spring annotation bug and inheritance enhance issue.
• Fix CPU accessor bug.

Backend

Performance improved, especially in CPU limited environment. 3x improvement in service mesh scenario(no trace) in 8C16G VM.
Significantly cost less CPU in low payload.

• Support database metric and SLOW SQL detection.
• Support to set max size of metadata query. And change default to 5000 from 100.
• Support ElasticSearch template for new feature in the future.
• Support shutdown Zipkin trace analysis, because it doesn't fit production environment.
• Support log type, scope HTTP_ACCESS_LOG and query. No feature provided, prepare for future versions.
• Support .NET clr receiver.
• Support Jaeger trace format, no analysis.
• Support group endpoint name by regax rules in mesh receiver.
• Support diable statement in OAL.
• Support basic auth in ElasticSearch connection.
• Support metric exporter module and gRPC implementor.
• Support >, <, >=, <= in OAL.
• Support role mode in backend.
• Support Envoy metric.
• Support query segment by service instance.
• Support to set host/port manually at cluster coordinator, rather than based on core settings.
• Make sure OAP shutdown when it faces startup error.
• Support set separated gRPC/Jetty ip:port for receiver, default still use core settings.
• Fix JVM receiver bug.
• Fix wrong dest service in mesh analysis.
• Refactor ScopeDeclaration annotation.
• Refactor register lock mechanism.
• Add SmartSql component for .NET
• Add integration tests for ElasticSearch client.
• Add test cases for exporter.
• Add test cases for queue consume.

UI

• RocketBot UI has been accepted and bind in this release.
• Support CLR metric.

Document

• Documents updated, matching Top Level Project requirement.
• UI licenses updated, according to RocketBot UI IP clearance.
• User wall and powered-by list updated.
• CN documents removed, only consider to provide by volunteer out of Apache.

All issues and pull requests are here

[coveralls]

Coverage remained the same at 16.009% when pulling 1525c05 on changelog into 660943a on master.