Add expertimental `optimisticKey` behind a flag (#35162) #1542

Job	Run time
Lint babel-plugin-react-compiler	26s
Jest babel-plugin-react-compiler	54s
Discover yarn workspaces	5s
Test make-read-only-util	24s
Test react-compiler-runtime	28s
Test react-mcp-server	22s
Test react-compiler-healthcheck	27s
Test react-forgive	43s
Test snap	21s
Test babel-plugin-react-compiler	1m 2s
Test eslint-plugin-react-compiler	39s
	5m 51s

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