Support casting of Float16 with other numeric types

[viirya]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

We support casting between various numeric types (signed/unsigned integers, floating), but for floating types, Float16 is not in supported list.

Describe the solution you'd like

Make sure Float16 is supported as like Float32/64 in numeric type casting.

Describe alternatives you've considered

Additional context

[tustvold]

label_issue.py automatically added labels {'arrow'} from #5139