refactor: move ProtocolHandler impl #6

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	40s
Android Build Only (aarch64-linux-android)	1m 11s
Checking docs	1m 4s
Android Build Only (armv7-linux-androideabi)	1m 6s
Checking fmt	29s
check_semver	22s
clippy_check	1m 32s
Cross Test (i686-unknown-linux-gnu)	55s
cargo deny	29s
codespell	7s
Minimal Supported Rust Version	1m 2s
CI Test Suite / Tests (ubuntu-latest, stable, all)	1m 17s
CI Test Suite / Tests (ubuntu-latest, stable, none)	1m 0s
CI Test Suite / Tests (ubuntu-latest, stable, default)	1m 0s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	1m 16s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	49s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	1m 9s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	1m 47s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	1m 6s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	1m 43s
	20m 4s

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