reactor: Mark .configure() private #41

Job	Run time
Test with C++20 modules enabled / test	2m 17s
Test with DPDK enabled / test	11m 37s
Test (clang++, C++20, debug) / test	6m 48s
Test (clang++, C++20, release) / test	5m 8s
Test (clang++, C++23, debug) / test	32m 22s
Test (clang++, C++23, dev) / test	4m 57s
Test (clang++, C++20, dev) / test	4m 25s
Test (clang++, C++23, release) / test	15m 21s
Test (g++, C++20, debug) / test	7m 39s
Test (g++, C++20, dev) / test	4m 32s
Test (g++, C++23, debug) / test	9m 1s
Test (g++, C++23, dev) / test	4m 13s
Test (g++, C++20, release) / test	5m 24s
Test (g++, C++23, release) / test	5m 21s
	1h 59m 5s

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