Exclude-elements doesn't work when taking screenshot of selected page part

[tkaik]

Version used

• AET 3.0.0

Context of the issue/feature

The exclude-elements feature of the screenshot collector doesn't work correctly when you configure it to take a screenshot of a selected page fragment (using css attribute) and also configure the exclude-elements attribute to exclude some page fragment from screen comparision -- the coordinates of elements to exclude are not computed correctly.

Steps to reproduce

1. Prepare a suite with screen collector with both css and exclude-elements attribute, e.g. <screen css="#content" exclude-elements=".dynamic1" />.
   The css attribute should point to element which does not start in the top-left corner (i.e. (0; 0) coordinates) of the page body. The exclude-elements attribute should point to element which is inside the element pointed by css attribute and it's displayed differently every time you refresh the page.
2. Run the suite and open the report - the report shows failure because of differences on element which should have been excluded.