feat: implement `FromStr` and `Display` for `Protocol` #8768

Job	Run time
coverage	33s
cargo-deny	24s
docs	33s
external-types (opentelemetry)	33s
lint	35s
external-types (opentelemetry-sdk)	31s
msrv (windows-latest, 1.75.0)	23s
test (ubuntu-latest, stable)	19s
msrv (ubuntu-latest, 1.75.0)	32s
test (ubuntu-latest, beta)	21s
external-types (opentelemetry-otlp)	31s
test (stable, windows-latest)	18s
external-types (opentelemetry-zipkin)	32s
test (stable, macos-latest)	19s
test (stable, ubuntu-22.04-arm)	24s
	6m 48s

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