Don't create the renderer in the constructor for infinite progressbar

This fixes the infinite progress bar code to not create the renderer inside the constrcutor. The old behaviour was not only a potential performance and memory leak and just seems generally incorrect from a best practices standpoint.

The tests had to be modified to actually render the object so this is a change in behaviour but I would not call it breaking given that I consider the old behaviour a incorrect and a bug.

widget/progressbarinfinite.go

@@ -193,7 +193,7 @@ func (p *ProgressBarInfinite) CreateRenderer() fyne.WidgetRenderer {
 // SetValue() is not defined for infinite progress bar
 // To stop the looping progress and set the progress bar to 100%, call ProgressBarInfinite.Stop()
 func NewProgressBarInfinite() *ProgressBarInfinite {
-	p := &ProgressBarInfinite{}
-	cache.Renderer(p).Layout(p.MinSize())
-	return p
+	bar := &ProgressBarInfinite{}
+	bar.ExtendBaseWidget(bar)
+	return bar
 }

widget/progressbarinfinite_test.go

@@ -27,12 +27,22 @@ func BenchmarkProgressbarInf(b *testing.B) {
 
 func TestProgressBarInfinite_Creation(t *testing.T) {
 	bar := NewProgressBarInfinite()
-	// ticker should start automatically
+
+	// ticker should be disabled until the widget is shown
+	assert.False(t, bar.Running())
+
+	win := test.NewWindow(bar)
+	win.Show()
+
+	// ticker should start automatically once the renderer is created
 	assert.True(t, bar.Running())
 }
 
 func TestProgressBarInfinite_Destroy(t *testing.T) {
 	bar := NewProgressBarInfinite()
+	win := test.NewWindow(bar)
+	win.Show()
+
 	assert.True(t, cache.IsRendered(bar))
 	assert.True(t, bar.Running())
 
@@ -46,6 +56,8 @@ func TestProgressBarInfinite_Destroy(t *testing.T) {
 
 func TestProgressBarInfinite_Reshown(t *testing.T) {
 	bar := NewProgressBarInfinite()
+	win := test.NewWindow(bar)
+	win.Show()
 
 	assert.True(t, bar.Running())
 	bar.Hide()