Handle Text Input Overflow

[willpatera]

Issue migrated from #6

Handle overflowing text within the Text Input UI Element.

• [x] upon selecting the text field, the caret and text text should scroll to the end (if overflowing the field width)
• [x] navigating text with caret should scroll the text so the caret is never invisible.

[willpatera]

Leaving open - many things to fix still.

• [x] fix text position/caret scroll on select after menu resize. Currently caret 'properly' scrolls to the end of the text on selection of the textfield. But if the menu gets resized, the clip start index needs to be shifted to show as much text as possible within the new max width of the text field.
• [x] fix highlighting for long overflowing text. When highlighting overflowing text with shift + left arrow the highlight area needs to be constrained within the textfield.size.x - x_spacer -- currently it overflows the bounds.
• [x] fix preview update. If typing fast the preview can not keep up with the speed of typing. Thus the text that you are typing is outside of textfield.size.x

[willpatera]

All done.