feat: Improved custom tracing span API #28

Job	Run time
Basic checks	54s
Build and publish artifacts and plugins locally	2m 26s
Run annotation processor tests	1m 45s
Run sbt test	3m 58s
Check service docker image contents	58s
Maven samples (shopping-cart-quickstart, true)	1m 8s
Maven samples (choreography-saga-quickstart, true)	1m 13s
Maven samples (doc-snippets, false)	48s
Maven samples (view-store, true)	1m 32s
Maven samples (spring-dependency-injection, true)	49s
Maven samples (event-sourced-customer-registry, true)	54s
Maven samples (event-sourced-counter-brokers, docker compose up -d, true)	1m 47s
Maven samples (event-sourced-customer-registry-subscriber, true, ./start-upstream.sh)	1m 22s
Maven samples (key-value-counter, true)	1m 0s
Maven samples (key-value-shopping-cart, true)	46s
Maven samples (key-value-customer-registry, true)	1m 1s
Maven samples (tracing, false)	42s
Maven samples (reliable-timers, true)	40s
Maven samples (transfer-workflow, true)	1m 0s
Maven samples (transfer-workflow-compensation, true)	51s
	25m 34s

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