Multiple target support to OverlayPanel

[mertsincan]

A overlay panel can be toggled by multiple target elements. Exp;

...
<Button type="button" label="Toggle" onClick={(e) => this.op.toggle(e)} />
<Button type="button" label="Toggle-2" onClick={(e) => this.op.toggle(e)} />

<OverlayPanel ref={(el) => this.op = el}>
    ...
</OverlayPanel>
...