Add sinkScope: LazyScope value

Renamed from "padPlace" to "sinkScope"

background: At the request of the physical implementation & design team,
            we needed a space to put the pad in one place.
            So I created a value called sinkScope.
            sinkScope default value is shell.

Add def sinkScope: LazyScope = shell in IOPlacedOverlay trait

Changed the existing sink scope from shell to sinkScope.
     in GPIOPlacedOverlay, I2CPlacedOverlay, JTAGDebugPlacedOverlay,
        PWMPlacedOverlay, SPIFlashPlacedOverlay, UARTPlacedOverlay