Consolidate error codes for lower level functions

[mkannwischer]

See, e.g,

mldsa-native/mldsa/src/sign.c

Lines 1199 to 1205 in 9a180a9

	/* mld_polyvecl_chknorm signals failure through a single non-zero error code
	* that's not yet aligned with MLD_ERR_XXX. Map it to MLD_ERR_FAIL. */
	if (mld_polyvecl_chknorm(z, MLDSA_GAMMA1 - MLDSA_BETA))
	{
	ret = MLD_ERR_FAIL;
	goto cleanup;
	}

Task

• Move normalization of error codes into lower level functions where possible