Test

Merge 'metrics: Internalize metric label sets' from Stephan Dollberg #931

Job	Run time
Test with C++20 modules enabled / test	11m 35s
Test with DPDK enabled / test	16m 1s
Test (clang++, C++20, debug) / test	10m 55s
Test (clang++, C++20, release) / test	8m 37s
Test (clang++, C++23, release) / test	16m 13s
Test (clang++, C++20, dev) / test	8m 6s
Test (clang++, C++23, debug) / test	10m 24s
Test (clang++, C++23, dev) / test	8m 20s
Test (g++, C++20, debug) / test	11m 35s
Test (g++, C++20, release) / test	9m 16s
Test (g++, C++23, debug) / test	11m 36s
Test (g++, C++20, dev) / test	7m 3s
Test (g++, C++23, dev) / test	6m 58s
Test (g++, C++23, release) / test	17m 47s
	2h 34m 26s

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