Tests that DOM.forceShowPopover determines the invoker correctly for implicit anchoring
\nTest 1: commandfor button acts as default invoker
Popover p1 top position: {
    description : 100
    type : number
    value : 100
}
\nTest 2: first popovertarget button acts as default invoker
Popover p2 top position: {
    description : 200
    type : number
    value : 200
}
\nTest 3: explicit invokerNodeId overrides default popovertarget button
Popover p2 top position: {
    description : 300
    type : number
    value : 300
}
\nTest 4: explicit invalid invokerNodeId returns an error
Error: invoker id not found