file: Use lighter access to map of fs-info-s #27

Job	Run time
Test with DPDK enabled / test	11m 26s
Test with C++20 modules enabled / test	2m 23s
Test (clang++, C++20, dev) / test	4m 42s
Test (clang++, C++20, debug) / test	6m 41s
Test (clang++, C++20, release) / test	5m 13s
Test (clang++, C++23, debug) / test	6m 57s
Test (clang++, C++23, dev) / test	4m 26s
Test (clang++, C++23, release) / test	5m 5s
Test (g++, C++20, debug) / test	7m 49s
Test (g++, C++20, release) / test	5m 24s
Test (g++, C++23, debug) / test	8m 30s
Test (g++, C++20, dev) / test	4m 37s
Test (g++, C++23, dev) / test	4m 31s
Test (g++, C++23, release) / test	6m 2s
	1h 23m 46s

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