Sorting by name does not work for > 10 variables from the same base

```julia
using MultivariatePolynomials
using TypedPolynomials

const X = @polyvar X[1:10]

julia> MultivariatePolynomials.monomials(X[1:10], 2)
ERROR: ArgumentError: Variables must be in order

julia> MultivariatePolynomials.monomials(X[1:9], 2)
# ok
```

Maybe the name should check for identical base variable?