fmpz_mat_snf_kannan_bachem can take any matrix #3163

Job	Run time
MinGW GCC (x0.5)	11m 28s
GCC build regression check (no tests)	5m 4s
macOS-M1, Clang (x3)	10m 2s
Alpine Linux, musl, 32-bit (assert, x1.5)	14m 2s
MSVC (x1)	9m 44s
Nemo.jl	18m 12s
Ubuntu Clang, BLAS and examples (x5)	12m 52s
Ubuntu GCC, Code Coverage (x10)	29m 27s
Ubuntu GCC with NTL (assert, x2)	8m 2s
	1h 58m 53s

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