fix bounding box function, get rid of extensions, copied from imported libraries

[ghost]

Before:

After:

As you can see, there are 2 bugs in current getBoundingBoxes implementation:

• Outer composable (column in our case) take full screen width, except of padding 20.dp, but bounding boxes are much far away from right than from left
• There is precision loose which you can find on screenshots for "filled blue" spans, so box for "the parts" are not aligned.

If you still need this "trim box to width" functionality, than maybe we can mix implementations, but better idea would be to create feature request to TextField composable (more precisely to TextLayoutResult) to return trimmed bounding boxes (for example with next function TextLayoutResult.getPathForRange(start, end, trim: Boolean)