v4.0-RC1

What's Changed

• clean CAT API interface
• a brand new embedded component container introduced, plexus container removed
• standardized client CAT_HOME, use ~/.cat as default CAT home directory
• remove unnecessary external jar dependencies, only netty left in maven compile scope
• rewrite client configuration management, make it much more adaptive and manageable
• rewrite client message construction to support multiple threading and asynchronous scenarios better
• introduce message pipeline mechanism to pre-process message
  typical scenario includes message filtering, sampling, aggregating, encoding, compressing, pooling and statistics etc
• separate metric out of trace message and standalone
• manage the generated source code in git version control
• rewrite all unit tests for better code quality and higher code coverage
• use github actions to publish client jar to maven central repository automatically (thanks goes to @power-lin)

NOTES: this is a BREAK version, it introduces some incompatible with 3.X version. The core API is remain unchanged, but the advanced API is changed and needs to re-integrate.

Full Changelog: 3.1.0...v4.0-RC1