Doc: Fix qdoc warnings

- Mark undocumented but existing functions with \c (instead of \l or \sa)
- Remove reference to functions I could no longer find
- Fix other broken links
- Fix reference to an image whose file format changed to WEBP
- Use {} instead of "" to mark alt text for images
- Add missing \a commands
- Add class name to a function name so that it can be found

Change-Id: I10655bb0356c7417ab0e14a3ce620930f4ee8349
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/progressindicator.cpp

@@ -200,7 +200,7 @@ ProgressIndicator::ProgressIndicator(ProgressIndicatorSize size, QWidget *parent
 /*!
     Changes the size of the progress indicator to \a size.
 
-    \sa indicatorSize
+    \sa ProgressIndicatorPainter::indicatorSize()
 */
 void ProgressIndicator::setIndicatorSize(ProgressIndicatorSize size)
 {
@@ -211,7 +211,7 @@ void ProgressIndicator::setIndicatorSize(ProgressIndicatorSize size)
 /*!
     Returns the size of the indicator in device independent pixels.
 
-    \sa indicatorSize
+    \sa ProgressIndicatorPainter::indicatorSize()
 */
 QSize ProgressIndicator::sizeHint() const
 {