Adjust the widgets fitting algorithm to mitigate over packing issue

If we are fitting more than one widgets / shortcuts on the same row,
we will only allow the total width to be n - 1 cells, where n is the
grid width in cells.

Test: Run WidgetsTableUtils robolectric test.
Bug: 189103942
Change-Id: I2f23cb08fe95d68562188cc7b1852d99d7093dc0