[Format][Docs] Describe C device interface on C data interface and C stream interface docs pages

[ianmcook]

Describe the enhancement requested

The following facts are not immediately obvious to readers of the C data interface and C stream interface docs pages:

• The C data interface is a CPU-only subset of the C device data interface.
• The C stream interface is a CPU-only subset of the C device stream interface.
• We will never remove the existing CPU-only C data/stream interfaces (because we must keep them to preserve compatibility with existing systems)...
• ... but when we add new structure definitions (for example as in GH-43631: [C][Format] Add ArrowAsyncDeviceStreamHandler interface #43632), we will add them only to the C device data/stream interfaces (to reduce duplication of efforts).
• In other words, the CPU-only C data/stream interfaces are in "maintenance mode."
• This will force developers that are currently using the CPU-only C data/stream interfaces and who wish to use the new structures to switch over to using the C device data/stream interfaces. This is simple enough to do.

To make this clearer, we should add note boxes to to CDataInterface.rst and CStreamInterface.rst to explain some of this and to link to CDeviceDataInterface.rst. The note boxes should clearly state that the CPU-only C data/stream interfaces are in "maintenance mode."

Component(s)

Documentation, Format