Run examples on host or device

[streeve]

Follow on to #617. Convert DefaultHostExecutionSpace to DefaultExecutionSpace and add mirrors as needed to ensure legal memory access. Consider keeping some/all of the data structure examples fully on the host (examples prior to mirror/deep_copy)

[streeve]

@lebuller can you start on this and let me know if you questions?

[dineshadepu]

I am happy to take this and give a PR on examples related to Cabana (core examples). Is that okay? @streeve

[streeve]

That would be great - to be clear changing from host-only will require copying data back and forth from the CPU and GPU with mirror copies in quite a few places (after data is created, when it's time to print back on the host, etc.)

[dineshadepu]

Thank you. I will convert one of the examples first and will ask for feedback so that I do it correctly.