[Grid] Migrate the main logic to Core with ConstrainSet

[jswong65]

Mark this as a WIP - Even though setters work properly, but it uses the ConstrainSet approach instead of LayoutParams

The main purpose of this PR is to migrate the main logic of the Grid Helper into core library. Tasks are accomplished in this PR:

1. created a new GridEngine file in core and migrate the main logic into it.
2. added a test file GridEngineTest.
3. Add more Demos, including row, column, row_in_column, and column_in_row.

Row

Column

column_in_row

row_in_column