[Material] [Android, iOS] Added Slider and ProgressBar

[mattleibow]

Description of Change

Added the Material versions of the ProgressBar and Slider.

Issues Resolved

• fixes [Material] Linear Progress Indicator #5008
• closes [Android Material] Linear Progress Indicator #5079
• fixes [Material] [Android, iOS] Slider Spec #5018

API Changes

Added the Material renderers for Slider and ProgressBar for Android and iOS.

The rules for the coloring are as follows:

• All default colors, then use the defaults
• A single color for ProgressBar.ProgressColor or Slider.MinimumTrackColor, then follow material: a single color throughout (including the slider thumb), but the background has an alpha
• A single background color for ProgressBar.BackgroundColor or Slider.MaximumTrackColor, then just set the background color
• Both progress and background, then throw material out and set colors explicitly
• A default slider thumb, then fall back to the primary color
• A specific thumb, then use that explicitly

Platforms Affected

• iOS
• Android

Behavioral/Visual Changes

New Material renderers.

Before/After Screenshots

	Android	iOS
Defaults
Height of 50
Primary color of Red
Primary and Background
All
All with 50% alpha

Testing Procedure

Loads of buttons and switches on the MaterialProgressBarGallery gallery or "[Material] ProgressBar & Slider Gallery".

PR Checklist

• Has automated tests
• Rebased on top of the target branch at time of PR
• Changes adhere to coding standard

[PureWeen]

Looks great! The testing page is awesome

It seems like some of the Color Pickers in the gallery should start on the left not the right. When you first move any of the settings the bars vanish because everything is cranked up to white by default so if you move anything then it all just vanishes

[PureWeen]

Failing tests unrelated

[paymicro]

[Android] All with 50% alpha

I think the lines should be without space.

[paymicro]

Looks great!

[mattleibow]

@paymicro thanks for pointing out the weird thing. I for got to mention it on this PR.
As far as I can see, this is not something that most people would do, and if they do, the shouldn't 😄Unless we are going to make time for a custom slider... in addition to the progress bar.