Fix a special case for button masks

[Sauermann]

In certain situations it is possible that in a Viewport the same mouse button is pressed twice in series without releasing it in between.
In this case, focus stealing should happen to ensure, that the mouse button is not sent unintentionally to the previously focused Control node.

resolve #89917

[akien-mga]

This seems to break CodeEdit unit tests:

./tests/scene/test_code_edit.h:3078:
TEST CASE:  [SceneTree][CodeEdit] completion
  [CodeEdit] autocomplete completion

./tests/scene/test_code_edit.h:3527: ERROR: CHECK( code_edit->get_code_completion_selected_index() == -1 ) is NOT correct!
  values: CHECK( 2 == -1 )

./tests/scene/test_code_edit.h:3528: ERROR: CHECK( code_edit->get_line(0) == "item_2" ) is NOT correct!
  values: CHECK( i == item_2 )

./tests/scene/test_code_edit.h:3539: ERROR: CHECK( code_edit->get_line(0) == "i" ) is NOT correct!
  values: CHECK( iT == i )

[Sauermann]

Adjusted unit-tests: for a mouse double click it is necessary that the mouse is released between the first and the second click.

[akien-mga]

Thanks!