Add hardcoded flint_mpn_aors_n for ARM and x86 #1613

Job	Run time
GCC build regression check (no tests)	1m 8s
Alpine Linux, musl, 32-bit (assert, x1.5)	14m 11s
macOS-M1, Clang (x3)	9m 0s
MinGW GCC (x0.5)	10m 36s
MSVC (x1)	25m 25s
macOS-x86 Clang with BLAS (x2)	13m 40s
Nemo.jl (temporary branch)	18m 13s
Ubuntu Clang with examples (x5)	12m 44s
Ubuntu GCC with NTL (assert, x2)	8m 43s
Ubuntu GCC, Code Coverage (x10)	30m 17s
	2h 23m 57s

Provide feedback