apps/cmp: improve -reqin option to read fallback public key from firs… #905

Job	Run time
compiler (gcc-7, ubuntu-20.04)	6m 34s
compiler (gcc-8, ubuntu-20.04)	7m 35s
compiler (gcc-9, ubuntu-20.04)	6m 22s
compiler (gcc-10, ubuntu-20.04)	7m 34s
compiler (gcc-11, ubuntu-22.04)	8m 36s
compiler (gcc-12, ubuntu-22.04)	6m 51s
compiler (gcc-13, ubuntu-22.04, ubuntu-toolchain-r/test)	7m 22s
compiler (clang-6.0, ubuntu-20.04)	1m 54s
compiler (clang-7, ubuntu-20.04)	1m 53s
compiler (clang-8, ubuntu-20.04)	2m 6s
compiler (clang-9, ubuntu-20.04)	8m 1s
compiler (clang-10, ubuntu-20.04)	6m 35s
compiler (clang-11, ubuntu-20.04)	6m 15s
compiler (clang-12, ubuntu-20.04)	6m 4s
compiler (clang-13, ubuntu-22.04)	6m 21s
compiler (clang-14, ubuntu-22.04)	8m 0s
compiler (clang-15, ubuntu-22.04, jammy)	6m 50s
compiler (clang-16, ubuntu-22.04, jammy)	8m 19s
	1h 53m 12s

Provide feedback