Refactor module structure #799

Job	Run time
cargo check (msrv) (android) (armv7-linux-androideabi)	25s
cargo clippy (windows-latest)	2m 6s
cargo check (msrv) (android) (aarch64-linux-android)	48s
cargo check (msrv) (windows-latest)	2m 1s
cargo clippy (macos-latest)	52s
cargo check (msrv) (android) (x86_64-linux-android)	42s
cargo clippy (android) (armv7-linux-androideabi)	1m 48s
cargo check (msrv) (macos-latest)	26s
cargo clippy (ubuntu-latest)	1m 2s
cargo check (msrv) (ubuntu-latest)	26s
cargo clippy (android) (aarch64-linux-android)	54s
cargo doc (windows-latest)	20s
cargo clippy (android) (x86_64-linux-android)	1m 48s
formatting	26s
cargo doc (macos-latest)	22s
cargo test (windows-latest)	32s
cargo doc (ubuntu-latest)	17s
cargo test (macos-latest)	30s
typos	4s
cargo test (ubuntu-latest)	34s
	16m 23s

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