reactor: Mark .configure() private #42

Job	Run time
Test with DPDK enabled / test	19m 48s
Test with C++20 modules enabled / test	9m 32s
Test (clang++, C++20, dev) / test	9m 52s
Test (clang++, C++20, debug) / test	11m 52s
Test (clang++, C++20, release) / test	10m 44s
Test (clang++, C++23, debug) / test	40m 18s
Test (clang++, C++23, dev) / test	12m 54s
Test (clang++, C++23, release) / test	12m 57s
Test (g++, C++20, debug) / test	15m 14s
Test (g++, C++20, release) / test	12m 33s
Test (g++, C++20, dev) / test	9m 11s
Test (g++, C++23, debug) / test	16m 34s
Test (g++, C++23, dev) / test	40m 7s
Test (g++, C++23, release) / test	15m 56s
	3h 57m 32s

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