2.0.0-release

Features:

[#6597] supports dolphinscheduler upgrade from 1.x to 2.0
[#6812] speed up the site loading when project exists multi process definitions
[#6763] remove the detection of dumplicate task names
[#6655] remove the registry monitor

Bug Fix:
[#6613] fix bug in task retry mechanism
[#6707] fix error when set up the global parameters in process defintion
[#6882] fix process cannt finish and its status always be running
[#6771] fix failover worker interrupt
[#6658] fix task code in bulk definition
[#6737] fix event handle twice in two thread pool
[#6682] replace task name with task code
[#6653] fix netty client create too many channels
[#6640] fix PROCESS_HOST_UPDATE_REQUST command donot be supported.
[#6591] fix improt process definition error