Add unit test for block-builder #9573

Job	Run time
Run integration tests (test-e2e)	29m 34s
Benchmark	7m 31s
Run integration tests (test-integration-poller)	10m 22s
Build	1m 53s
Run integration tests (test-e2e-deployments)	29m 29s
Run integration tests (test-e2e-serverless)	7m 16s
Lint	3m 22s
Run Unit Tests (test-with-cover-pkg)	3m 27s
Run Unit Tests (test-with-cover-tempodb)	15m 57s
Run Unit Tests (test-with-cover-tempodb-wal)	11m 23s
Build technical documentation	19s
Run Unit Tests (test-with-cover-others)	12m 31s
Check jsonnet & tempo-mixin	51s
Vendor check	1m 21s
	2h 15m 16s

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