feat: FlowControl: add FromStr impl #333

Job	Run time
cargo-deny (advisories)	26s
lint	37s
cargo-deny (bans licenses sources)	19s
aarch64-apple-darwin / build	1m 44s
aarch64-apple-ios / build	1m 27s
aarch64-unknown-linux-gnu / build	40s
aarch64-unknown-linux-musl / build	1m 6s
arm-linux-androideabi / build	39s
armv7-linux-androideabi / build	59s
i686-pc-windows-msvc / build	4m 2s
i686-unknown-linux-gnu / build	39s
i686-pc-windows-gnu / build	3m 57s
i686-unknown-linux-musl / build	1m 31s
msrv-arm-linux-androideabi / build	4m 8s
msrv-aarch64-apple-darwin / build	4m 9s
msrv-x86_64-pc-windows-msvc / build	6m 6s
msrv-x86_64-unknown-freebsd / build	4m 7s
msrv-x86_64-unknown-linux-gnu / build	3m 59s
msrv-x86_64-unknown-linux-musl / build	3m 59s
msrv-x86_64-unknown-netbsd / build	5m 39s
x86_64-apple-darwin / build	1m 22s
x86_64-pc-windows-gnu / build	5m 2s
x86_64-pc-windows-msvc / build	4m 5s
x86_64-unknown-freebsd / build	51s
x86_64-unknown-linux-gnu / build	38s
x86_64-unknown-linux-musl / build	54s
x86_64-unknown-netbsd / build	34s
	1h 3m 39s

Provide feedback