feat(spool): Introduce in-memory `EnvelopeBuffer` as alternative to the old spooler #14746

Job	Run time
Test (macos-latest)	2m 34s
Test (macos-latest)	2m 34s
Lint Rust Default Features	1m 30s
Lint Rust Default Features	1m 30s
Lint	3m 35s
Lint	3m 35s
Test (windows-latest)	4m 46s
Test (windows-latest)	4m 46s
Test All Features (ubuntu-latest)	4m 6s
Test All Features (ubuntu-latest)	4m 6s
Integration Tests	13m 33s
Integration Tests	13m 33s
Setup build metadata	1s
Setup build metadata	1s
Test Python	1m 7s
Test Python	1m 7s
Build Relay Binary (relay, x86_64-unknown-linux-gnu)	8m 5s
Build Relay Binary (relay, x86_64-unknown-linux-gnu)	8m 5s
Build Docker Image (relay)	41s
Build Docker Image (relay)	41s
Sentry-Relay Integration Tests	9m 46s
Sentry-Relay Integration Tests	9m 25s
Publish Relay to DockerHub	0s
Publish Relay to DockerHub	0s
self-hosted-end-to-end	14m 17s
self-hosted-end-to-end	14m 17s
Upload build artifacts to gocd	0s
Upload build artifacts to gocd	0s
Publish Relay to GCR	0s
Publish Relay to GCR	0s
	2h 7m 41s

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