[SDL 0027] Increase Specificity of Handler Events

[theresalech]

Proposal: Increase Specificity of Handler Events

The purpose of this proposal is to make notification handlers more specific. Currently, the developer is required to know how to cast a notification parameter within the handler in order to properly use that notification. This proposal changes handlers to provide greater specificity on all RPCs that support them, as well as to separate out button handlers into two separate types. This will involve major version changes to remove old versions of the handlers that will no longer be supported.

Review: smartdevicelink/sdl_evolution#89

SDLC Steering Committee Decision:

The Steering Committee has accepted this proposal, given the following revisions: the SDLRPCButtonEventNotificationHandler and SDLRPCButtonPressNotificationHandler would be combined into one handler instead, with the signature: typedef void (^SDLButtonActionNotificationHandler)(__nullable SDLOnButtonPress *buttonPress, __nullable SDLOnButtonEvent *buttonEvent);