[PC3] Refactor TextField

Compensate for inset in implicit size.

Set padding to 0 if background is not present or does not have the margins property.

Use more of TextField's properties for setting the appearance.

Fix input alignment in RTL layouts.

Make placeholder text renderType match TextField's.

Use clear() instead of text = "".

Use colorGroup to set colors instead of deprecated properties.

Use disableTextColor for placeholderTextColor.

Reduce background to 2 elements and set implicit size like most controls.

Set anchors.rightMargin of inlineButtonRow to background.margins.right instead of using smallSpacing, which may be less than or greater than the theme's right margin.