Update CHANGELOG for v1.0.0 #4085

Job	Run time
Python Client Test	1m 2s
Lint	1m 53s
Build Operator Binaries and Docker Images	5m 51s
Build Apiserver, CLI Binaries and Docker Images	3m 9s
Compatibility Test - 2.6.3	11m 40s
Compatibility Test - 2.5.0	10m 15s
Compatibility Test - 1.13.0	6m 23s
Compatibility Test - 2.4.0	11m 53s
Compatibility Test - Nightly	19m 44s
Compatibility Test - 2.7.0	12m 12s
	1h 24m 2s

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