feat(hydroflow_plus): push down persists and implement Pi example (#1… #477

Job	Run time
pre_job	7s
macos-universal (universal2-apple-darwin)	8m 39s
linux (x86_64-unknown-linux-gnu)	4m 20s
linux-cross (aarch64-unknown-linux-gnu, aarch64)	3m 33s
linux (i686-unknown-linux-gnu)	4m 21s
linux-cross (armv7-unknown-linux-gnueabihf, armv7)	3m 41s
windows (x86_64-pc-windows-msvc, x64)	9m 26s
windows (i686-pc-windows-msvc, x86)	11m 14s
windows (aarch64-pc-windows-msvc, x64)	13m 47s
Release	0s
	59m 8s

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