fix(cts): Generate non-zero zp values for MATMUL

The Matmul quant gen function was receiving a list of datatypes and not handling them correctly, leading to all zero-point values generated as 0.

While this commit fixes that, it changes some of the tests as setting the zp min/max changes the rng. This changes the generation of the --random-const-inputs arg, as it uses the same rng generator.

Signed-off-by: Madeleine Dunn madeleine.dunn@arm.com