refactor(sdk): change SpanProcessor::on_end to take &mut FinishedSpan #11070

Job	Run time
lint	1m 54s
cargo-deny	1m 10s
msrv (ubuntu-latest)	3m 45s
build-examples	1m 30s
coverage	2m 27s
docs	1m 50s
msrv (windows-latest)	7m 44s
external-types (opentelemetry-sdk)	41s
external-types (opentelemetry-otlp)	1m 14s
test (stable, windows-latest)	2m 19s
cargo-shear	3m 53s
external-types (opentelemetry-zipkin)	1m 10s
external-types (opentelemetry)	32s
test (stable, ubuntu-24.04-arm)	2m 1s
test (stable, macos-latest)	2m 23s
test (ubuntu-latest, beta)	2m 17s
test (ubuntu-latest, stable)	2m 18s
	39m 8s

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