fix(spans): Optional exclusive time #14384

Job	Run time
Lint	2m 52s
Setup build metadata	1s
Lint Rust Default Features	1m 15s
Test All Features (ubuntu-latest)	2m 54s
Test (macos-latest)	2m 55s
Integration Tests	2m 54s
Test (windows-latest)	2m 43s
Test Python	1m 6s
Build Relay Binary (relay, x86_64-unknown-linux-gnu)	2m 42s
Build Docker Image	1s
Publish Relay to DockerHub	1s
Sentry-Relay Integration Tests	1s
Publish Relay to GCR	1s
Upload build artifacts to gocd	1s
self-hosted-end-to-end	1s
	19m 28s

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