coroutine/generator: reimplement generator #590

Job	Run time
Test with C++20 modules enabled / test	11m 24s
Test with DPDK enabled / test	22m 51s
Test (clang++, C++20, debug) / test	15m 50s
Test (clang++, C++20, dev) / test	16m 17s
Test (clang++, C++20, release) / test	15m 51s
Test (clang++, C++23, debug) / test	16m 9s
Test (clang++, C++23, dev) / test	17m 20s
Test (clang++, C++23, release) / test	15m 22s
Test (g++, C++20, debug) / test	18m 6s
Test (g++, C++20, dev) / test	11m 47s
Test (g++, C++20, release) / test	15m 29s
Test (g++, C++23, debug) / test	18m 23s
Test (g++, C++23, dev) / test	11m 46s
Test (g++, C++23, release) / test	16m 23s
	3h 42m 58s

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