fix(span_processor): only call on_start with recording spans#3011

cijothomas merged 2 commits intoopen-telemetry:mainopen-telemetry/opentelemetry-rust:mainfrom

paullegranddc:paullgdc/span_processor/pass_only_recording_spanspaullegranddc/opentelemetry-rust:paullgdc/span_processor/pass_only_recording_spansCopy head branch name to clipboard