Bluetooth: Controller: Match Central roles for BT_CTLR_CENTRAL_SPACING

Find and match only Central role ticker when applying the
BT_CTLR_CENTRAL_SPACING value.

Use the EVENT_TICKER_RES_MARGIN_US value as +/- jitter
margin when ticker advanced scheduling is used to group
radio events.

When using CONFIG_BT_CTLR_CENTRAL_SPACING, do not add the
+/- jitter to the ticks_slot.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>