refactor: hide or remove unused code. #403

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	49s
check_semver	1m 9s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	1m 56s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	1m 38s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	1m 32s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	1m 38s
CI Test Suite / Tests (ubuntu-latest, stable, default)	1m 10s
clippy_check	1m 30s
cargo deny	27s
CI Test Suite / Tests (ubuntu-latest, stable, none)	1m 29s
Checking docs	59s
codespell	7s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	1m 57s
Minimal Supported Rust Version	1m 17s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 1s
Checking fmt	31s
Cross Test (i686-unknown-linux-gnu)	1m 19s
Android Build Only (armv7-linux-androideabi)	1m 11s
Android Build Only (aarch64-linux-android)	1m 10s
CI Test Suite / Tests (ubuntu-latest, stable, all)	1m 30s
	25m 20s

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