Windows: File URL issues in declarative autotests

Some declarative autotests have issues with file URLs in Windows due to the drive letter. The problematic tests are:

These tests fails two cases due to incorrect file URL when checking some of the error results. In windows file URLs look like this: "file:///C:/foo/bar" whereas the test expects "file://C:/foo/bar":
tst_qqmlecmascript
tst_QQuickLoader

Tests failing because they are using testFile() somewhere where they should use testFileUrl():
tst_rendernode
tst_qquickfontloader
tst_QQuickGridView
tst_QQuickItemLayer
tst_qquickpositioners

Not using shared util functions at all for data file resolving:
tst_QQuickMultiPointTouchArea