[SDL 0342] Remove Policy Mode Option From SDL Core

Proposal: [Remove Policy Mode Option From SDL Core](https://github.com/smartdevicelink/sdl_evolution/blob/master/proposals/0342-remove-policy-mode-option-from-sdl-core.md)

> The goal of this proposal is to remove the `EXTENDED_POLICY` build option from SDL Core, reducing support only to `EXTERNAL_PROPRIETARY` policies.

Review: https://github.com/smartdevicelink/sdl_evolution/issues/1172