feat: apply type promotion rules according to the device context

[kgryte]

This PR:

• closes Device-specific type promotion rules #672 by clarifying that device info must be taken into account when applying type promotion rules in result_type and can_cast. As not all devices can support all data types, both functions need to explicitly account for whether an array or dtype can be cast and/or promoted to a desired dtype on a given device.
• when provided only dtypes, both functions are required to only consider the full type promotion graph.
• when at least one argument is an array, both functions must account for device capabilities.
• for result_type, if two or more array arguments belong to separate devices, behavior is left unspecified and thus implementation-dependent.