Create generic `SerializeAsOptional` type for Pydantic #3462

Job	Run time
Test (ubuntu-22.04, 3.10)	1m 47s
Test (ubuntu-22.04, 3.11)	1m 56s
Test (ubuntu-22.04, 3.12)	1m 47s
Test (windows-2022, 3.10)	3m 16s
Test (windows-2022, 3.11)	3m 38s
Test (windows-2022, 3.12)	4m 28s
publish-dev-docs-from-pr	25s
publish-docs-from-main	0s
Publish snapshot to TestPyPI / Publish snapshot	32s
	17m 49s

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