Update StepperControl.Images

[mpospese]

1. Update package to require latest YCoreUI 1.7.0+
2. add override of renderingMode to StepperControl.Images and return .alwaysTemplate.
3. add assert to Images unit test that XCTAssertEqual($0.image.renderingMode, .alwaysTemplate) to confirm.
4. remove calls to .withRenderingMode(.alwaysTemplate) from the three default images (now handled by Images)
5. these images now scale with Dynamic Type! Test this behavior and if problematic (they did not scale before), override Images.textStyle to return nil (and add an assert to the unit test about it) to disable the scaling.