Parallel integrand evaluation [Feature Req.]

I need a pure-julia integration library that support multi-dimensional, vector valued integrands **and** batch integrand evaluation. HCubature.jl hits all these criteria except for batch integrand evaluation as in [Cubature.jl](https://github.com/JuliaMath/Cubature.jl). Is adding a vectorized method on the horizon?

Start by reviewing HCubature.jl's existing integrand interface and the batch-evaluation API in Cubature.jl, both referenced in the issue. The work is complete when HCubature.jl supports batch evaluation for its multidimensional, vector-valued integrands with suitable coverage of the requested behavior.

Written by the indexing model from the issue text.