[Types] Change SchemaTypeOptions.index to use IndexDirection?

[hasezoey]

Basically what the title says, currently SchemaTypeOptions.index uses a custom definition of all index options, which could just as easily be used from IndexDirection to have it in one place for maintainability, is there any reason why SchemaTypeOptions.index uses a custom definition over IndexDirection?

[vkarpov15]

Nope, no particular reason that I'm aware of. Feel free to give this a shot.

[hasezoey]

done with #12482