Summarized todos for #2441

[chickenlj]

This issue is a collection of todos extracted from #2441

• Find a better name for global package, possible names 'cfg' , 'gConfig', _global, etc.
• Move XxxOption definition in global package to separate packages Move XxxOption definition in global package to separate packages #2446
  • protocol
  • registry
  • metrics
  • config-center
  • metadata
  • logger
  • metrics & tracing
  • tls, custom, and profile will not be supported in the first release
• Decide params that should be put in CallOption, timeout, and more? Assemble CallOptions into RpcInvocation #2448
  • timeout
  • retries
  • xxx?
• Examine properties in various Configs, like ServerOption.FilterConf, etc.
• Mechanism for passing extra headers and trailers feat: Triple protocol unique metadata #2435
• Completely delete dubbo3 and grpc packages
• RefreshService? reflectionService and healthService
• Simplified version of dubbo.WithRegistry(), with default key support. Simplified version of dubbo.WithRegistry(), with default key support.  #2444
• Unify naming of server.WithRegistry(id, ...) and server.WithRegistryIds() Simplified version of dubbo.WithRegistry(), with default key support.  #2444

[chickenlj]

#2443