Update rust re-hydration code to pyo3 0.21 #567

Job	Run time
macos (x86_64)	36s
sdist	11s
linux (x86_64)	1m 4s
macos (aarch64)	46s
changes	4s
linux (x86)	1m 6s
linux (aarch64)	1m 31s
windows (x64)	2m 19s
linux (armv7)	1m 30s
windows (x86)	1m 27s
linux (s390x)	1m 23s
linux (ppc64le)	1m 23s
Build and push base postgres image	0s
Build and push base pyrust	0s
test	0s
	13m 20s

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