[SDL 0159] Static SDL Icon Names Enum

[theresalech]

Proposal: Static SDL Icon Names Enum

This proposal is to create a strongly typed enum for static SDL icon names. This will make it easier for developers to use these icons in their SDL apps.

Review: smartdevicelink/sdl_evolution#463

Steering Committee Decision:

The Steering Committee agreed to accept this proposal. It was clarified that this proposal is specific to the existence of an enum in the proxies that matches the hex values in the list of agreed upon static icons, and that the list of required static icons will be finalized via the SDLC's review of the Core Certification Guidelines.

[theresalech]

Closed via #1035