Support fragmenting non-overflowing table when necessary

[kwkbtr]

• There are some cases where fragmenting the table is necessary even if the table itself does not overflow. For example, if a figure element wrapping the table has some block-end padding and the border edge of the figure overflows the column, the figure element should be fragmented. However, since it is not allowed to fragment the figure element between the padding and the table element, the fragmentation should occur inside the table. In such a case, it is necessary that BreakPositions are inserted inside the table.
• In this PR, a new BreakPosition 'EntireTableBreakPosition' is introduced. An EntireTableBreakPosition is inserted when a table does not overflow at the initial layout. It is a kind of dummy BreakPosition, i.e., when it is chosen as used for fragmentation, it registers a FragmentLayoutConstraint (EntireTableLayoutConstraint), which triggers re-layout of the column. In this re-layout, BreakPositions are inserted inside the table so that the table can be fragmented.
• This PR reverts Always layout a table twice so that BreakPositions are inserted appropriately #384.