Google Pixel 3: new device

Add support for the Google Pixel 3 based on Petr Hodina's original device packages, and @Drakulix 's recent work getting support into the sdm845 kernel.

Support status is similar to other SDM845 devices, however audio support is missing and battery status reporting may be inaccurate (since we don't support the additional fuel gauge chip on the device).

This depends on !5486 (merged) being updated and merged.