Add Popover menu component

.changeset/tame-mayflies-move.md

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+---
+'@sumup/circuit-ui': major
+---
+
+Replaced the old Popover component with a new one. It uses Popper v2 and comes with a refreshed component API.

packages/circuit-ui/components/Popover/Popover.docs.mdx

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+import { Status, Props, Story } from '../../../../.storybook/components';
+import { Popover } from '@sumup/circuit-ui';
+
+# Popover
+
+Popover menus are a common pattern to display a list of subsequent action options, when interacting with an actionable component.
+
+<Story id="popover-base" />
+<Props of={Popover} />
+
+- Triggers of Popover can be primary, secondary, tertiary buttons, an overflow icon, or components with embedded buttons such as the [ImageInput component](Forms/ImageInput).
+- Each Popover action item is represented by an appropriate HTML element (button or a).
+- If needed the dividing line can be used to separate Popover action items.
+- The leading icon is optional.
+- The Popover is powered by React Popper [https://popper.js.org/docs/v2/] which means you can easily change the Popover placement by simply passing the placement prop.
+
+## Usage guidelines
+
+- **Do** use clear, concise and actionable labels for Popover items
+- **Do** always think about the priority of the action option to be taken and put the option order in logical order
+
+<Story id="popover-icon-trigger" />
+<Story id="popover-item-base" />