[video][PVR] Info dialogs: Add support for default play action

[ksooo]

Video, PVR recordings and PVR guide dialogs offer "play" buttons. This PR adds support for default play action for these buttons, means, the button will act according to the settings value.

Runtime-tested on macOS and android, latest Kodi master.

@enen92 @phunkyfish mind taking a look at the code changes?

[enen92]

Something for later: instead of returning a bool in Process() consider returning a status "code" (e.g. from an enum class) so that you don't need to expose m_userCancelled

[ksooo]

instead of returning a bool in Process() consider returning a status "code"

Idea was, that processing can be successful or not, independently of user cancelled. An enum to model all possible permutations can be tricky (later, in case more "status" come into play). Maybe the method should return a tuple in the future.