Add "Edit QuickTabs instance" contextual link

J Prequested to merge
issue/quicktabs-3606816:3606816-add-edit-quicktabs into 4.0.x

Adds quicktabs.links.contextual.yml declaring the link and attaches #contextual_links in QuickTabsInstance::getRenderArray() so it appears on all QT instances regardless of rendering context.

Closes #3606816

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