Set edgeMarginPx back to 8dp.

With the new grid changes, it was set to 16dp but this caused an issue
where the workspace page spacing was too large. To "restore" the original
page spacing we set it back to 8dp. This caused an issue where the
pages began to overlap.

This CL changes the edgeMarginPx back to 8dp, and then adds the additional
8dp to the padding of the CellLayout.

Bug: 63590728
Change-Id: Ie968d8bd81de19c726f73581d6609e3bc486c5ca

src/com/android/launcher3/Workspace.java

@@ -666,6 +666,10 @@ public class Workspace extends PagedView
         newScreen.setOnLongClickListener(mLongClickListener);
         newScreen.setOnClickListener(mLauncher);
         newScreen.setSoundEffectsEnabled(false);
+
+        int paddingLeftRight = mLauncher.getDeviceProfile().cellLayoutPaddingLeftRightPx;
+        newScreen.setPadding(paddingLeftRight, 0, paddingLeftRight, 0);
+
         mWorkspaceScreens.put(screenId, newScreen);
         mScreenOrder.add(insertIndex, screenId);
         addView(newScreen, insertIndex);