refactor(hydroflow_plus): move `HfCompiled` and friends to a module (… #916

Job	Run time
pre_job	6s
linux (x86_64-unknown-linux-gnu)	3m 23s
macos-universal (universal2-apple-darwin)	3m 58s
linux-cross (aarch64-unknown-linux-gnu, aarch64)	3m 26s
linux (i686-unknown-linux-gnu)	4m 42s
linux-cross (armv7-unknown-linux-gnueabihf, armv7)	3m 55s
windows (x86_64-pc-windows-msvc, x64)	11m 6s
windows (i686-pc-windows-msvc, x86)	12m 1s
windows (aarch64-pc-windows-msvc, x64)	13m 39s
Release	0s
	56m 16s

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