Detect when tap target is covered

[passsy]

await act.tap(button); just got way more helpful in two cases:

tap target covered by another widget

Shows a useful diagram when a widget can't be tapped because it is covered by another widget consuming the tap events.

Selector 'Widget with text contains text "Press Me"' can not be tapped directly, because another
widget (Listener) inside Padding is completely covering it and consumes all tap events.

Try tapping the Padding which contains 'Widget with text contains text "Press Me"' instead.

Example:
  // BAD: Taps the Text inside ElevatedButton
  WidgetSelector<AnyText> selector = spot<ElevatedButton>().spotText('Tap me');
  await act.tap(selector);

  // GOOD: Taps the ElevatedButton which contains text 'Tap me'
  WidgetSelector<ElevatedButton> selector = spot<ElevatedButton>().withChild(spotText('Tap me'));
  await act.tap(selector);

(Cover - Received tap event)             (Target for tap, below Cover)
Listener                                 RichText
RawGestureDetector                       Text
GestureDetector                           │
Semantics                                 │
DefaultSelectionStyle                     │
Builder                                   │
MouseRegion                               │
Semantics                                 │
_FocusInheritedScope                      │
Focus                                     │
_ActionsScope                             │
Actions                                   │
_ParentInkResponseProvider                │
_InkResponseStateWidget                   │
InkWell                                   │
DefaultTextStyle                          │
AnimatedDefaultTextStyle                  │
_InkFeatures-[GlobalKey#7028f ink render  │
NotificationListener<LayoutChangedNotifi  │
PhysicalModel                             │
AnimatedPhysicalModel                     │
Material                                  │
Positioned                                │
 │ ┌──────────────────────────────────────┘
Stack (file:///Users/pascalwelsch/Projects/passsy/spot/test/act/find_tappable_area_test.dart:242:14)
Padding
(file:///Users/pascalwelsch/Projects/passsy/spot/test/act/find_tappable_area_test.dart:240:12)

When the exception was thrown, this was the stack:
#0      Act._detectCoverWidget (package:spot/src/act/act.dart:590:5)
#1      Act._throwHitTestFailureReport (package:spot/src/act/act.dart:310:5)
#2      Act.tap.<anonymous closure>.<anonymous closure> (package:spot/src/act/act.dart:97:11)
#3      _alwaysPropagateDevicePointerEvents (package:spot/src/act/act.dart:670:17)
#4      Act.tap.<anonymous closure> (package:spot/src/act/act.dart:83:14)
#7      TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:71:41)
#8      Act.tap (package:spot/src/act/act.dart:82:27)
#9      main.<anonymous closure> (file:///Users/pascalwelsch/Projects/passsy/spot/test/act/find_tappable_area_test.dart:181:15)
<asynchronous suspension>
#10     testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:183:15)
<asynchronous suspension>
#11     TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:1017:5)
<asynchronous suspension>
<asynchronous suspension>
(elided 3 frames from dart:async and package:stack_trace)

tap target is 0x0 pixels

Also shows a useful error when the size of a widget is 0x0

ElevatedButton can't be tapped because it has size Size(0.0, 0.0).
SizedBox.shrink forces ElevatedButton to have the size Size(0.0, 0.0).
SizedBox.shrink file:///Users/pascalwelsch/Projects/passsy/spot/test/act/act_test.dart:335:29

When the exception was thrown, this was the stack:
#0      Act._detectSizeZero (package:spot/src/act/act.dart:503:7)
#1      Act._throwHitTestFailureReport (package:spot/src/act/act.dart:309:5)
#2      Act.tap.<anonymous closure>.<anonymous closure> (package:spot/src/act/act.dart:97:11)
#3      _alwaysPropagateDevicePointerEvents (package:spot/src/act/act.dart:670:17)
#4      Act.tap.<anonymous closure> (package:spot/src/act/act.dart:83:14)
#7      TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:71:41)
#8      Act.tap (package:spot/src/act/act.dart:82:27)
#9      actTests.<anonymous closure>.<anonymous closure> (file:///Users/pascalwelsch/Projects/passsy/spot/test/act/act_test.dart:349:17)

[danielmolnar]