Extend factorization to polynomials with more general coefficients.

I would love to compute the primary decomposition of the following ideal:

```
K = frac (QQ[k1,k2,k3,k4,k5,k6,k7,k8,k9,k10,k11,k12])
R = K[x1,x2,x3,x4,x5,x6,x7,x8,x9]
f1=-k1*x1*x2+k2*x3+k12*x9
f2=-k1*x1*x2+(k2+k3)*x3-k4*x2*x4+(k5+k6)*x5
f3=k1*x1*x2-(k2+k3)*x3
f4=k3*x3-k4*x2*x4+k5*x5+k9*x8-k10*x4*x7+k11*x9
f5=k4*x2*x4-(k5+k6)*x5
f6=k6*x5-k7*x6*x7+k8*x8
f7=-k7*x6*x7+(k8+k9)*x8-k10*x4*x7+(k11+k12)*x9
f8=k7*x6*x7-(k8+k9)*x8
f9=k10*x4*x7-(k11+k12)*x9
I=ideal(f1,f2,f3,f4,f5,f6,f7,f8,f9)
primaryDecomposition I
```

but unfortunately, we can't even factor polynomials in `R` since it has a fraction field as the coefficient field.

This issue is a feature request: What would be necessary to get this functionality in Macaulay2?

Start by reproducing the example with `frac`, `ideal`, and `primaryDecomposition`, then isolate the factorization failure for the fraction-field coefficient ring `K`. Read the existing factorization and fraction-field entry points; done means polynomials over `R` can be factored and the example's primary decomposition can be computed.

Written by the indexing model from the issue text.