TextField improvements

- Fix shrink-wrapping conflict with expands property.
- Fix text field model not calculating text field height properly for shrink-wrapping.
- Allow min lines and max lines input fields to clear.
- Fix shrink-wrap height calculation being affected by isDense property.

Author: BirjuVachhani

lib/src/api/utils.dart

@@ -43,6 +43,9 @@ abstract class ITextSizeCalculator {
   /// Returns The distance to the [baseline] of a defined [TextNode].
   /// The details are dependant on the implementation.
   double computeDistanceToActualBaseline(CTextBaseline baseline);
+
+  /// Returns the line height of a single line of text.
+  double getLineHeight();
 }
 
 /// Defines different styling options for a widget.