Refactor: Use to_writer/from_reader across the codebase #6146

Job	Run time
Check	24s
coverage	9m 32s
Lints (beta)	15s
test (beta)	1m 32s
test_all_features	12m 56s
test (stable)	1m 27s
Check if wasm-pack builds a valid package for the sourmash crate	1m 25s
test (windows)	3m 1s
test (macos)	1m 17s
Lints (stable)	7s
Check if cbindgen runs cleanly for generating the C headers	8m 0s
minimum_rust_version	6m 43s
Publish (on tags, dry-run otherwise)	5m 27s
Run tests under wasm32-wasi	1m 7s
	53m 13s

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