recovery: Remove SetColor, and other refactoring for WearUI

The only difference from SetColor in ScreenRecoveryUI is the that the
LOG messages have slightly different colors. That's not enough to
warrant a duplicate function. So this patch removes SetColor and uses
the parent class version.

This patch also moves the DrawTextLine* functions into ScreenRecoveryUI
since they're mostly the same. It also moves char_width and char_height
into the class instead of keeping them as static variables.

Bug: 27407422
Change-Id: I30428c9433baab8410cf710a01c9b1c44c217bf1