UserMenu Avatar onClick overrides the open behavior

[joebochill]

Describe the bug

If you put a onClick event on the Avatar that is passed into a UserMenu, that prop overrides the onClick behavior that is set up to open the menu.

What is the expected behavior?

The user-supplied onClick should be merged with the internal click handler

What are the steps to reproduce?

1. Add a UserMenu to a project
2. Add a onClick prop to the Avatar, e.g., <Avatar onClick={() => console.log('clicked')}>AB</Avatar>
3. Click the avatar
4. Observe that the menu is not opened and only the user-supplied click callback is executed

Anything else to add?

This is caused because we spread the user supplied Avatar props after defining the onClick prop (https://github.com/pxblue/react-component-library/blob/dev/components/src/core/UserMenu/UserMenu.tsx#L140). This causes the user-supplied onClick prop to overwrite what we set on the line above. The spread should come before the onClick.