Refactor UpgradeStrategy to UpgradeSpec.Type #6915

Job	Run time
Build Ray Kubectl plugin	2m 59s
Build Apiserver and Docker Images	3m 30s
Build Operator Binaries and Docker Images	6m 7s
Build security proxy Binaries and Docker Images	1m 53s
Lint (pre-commit)	3m 16s
Python Client Test	1m 5s
Compatibility Test - 2.9.0	10m 23s
Compatibility Test - 2.7.0	11m 36s
Compatibility Test - Nightly	9m 5s
Compatibility Test - 2.8.0	7m 19s
	57m 13s

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