VM/SS disk cache controls

[et1975]

Would be good to expose Data and OS disks' cache property

[Larocceau]

Hi @et1975! Thanks for pointing this out! We might pick this up in the near future. If you're willing to have a go at doing it yourself, we'll be happy to assist if you have any questions.

[et1975]

I was going to PR this, but it turned out that the defaults match what I need 😂. They are also dependent on the disk type, surfacing this correctly in the DSL might be a bit tricky.