fix(findComponent): allow finding top-level component

[xanf]

Let's assume following rendering structure:

flowchart LR
    RootComponent:::cmp --> NestedComponent:::cmp --> d(div.someclass):::dom
    classDef cmp fill:blue,color:white;
    classDef dom fill:darkgreen,color:white;

In this case

mount(RootComponent).find('.some-class').find(NestedComponent).exists() // true
mount(RootComponent).find('.some-class').find(RootComponent).exists() // false

This is because __vueParentComponent will point to component who actually rendered dom node
To fix this we traverse ancestors of __vueParentComponent while their vnode.element is equal to current dom node and use resulted vue component as base for our search

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