Speedup DistinctString and ScopedDistinctString collectors #9094

Job	Run time
Benchmark	9m 30s
Build	1m 45s
Run integration tests (test-e2e)	19m 48s
Lint	3m 4s
Run integration tests (test-integration-poller)	9m 21s
Run Unit Tests (test-with-cover-pkg)	3m 0s
Run integration tests (test-e2e-deployments)	12m 54s
Run Unit Tests (test-with-cover-tempodb)	16m 0s
Run integration tests (test-e2e-serverless)	6m 56s
Vendor check	1m 22s
Run Unit Tests (test-with-cover-tempodb-wal)	10m 45s
Run Unit Tests (test-with-cover-others)	12m 28s
Build technical documentation	20s
Check jsonnet & tempo-mixin	50s
	1h 48m 3s

Provide feedback