[707] - Fix edge case where the dropping a tile as last element does not save

[apandura-tibco]

Description

I have removed dependency of flag CdkDragDrop.isPointerOverContainer to know if the drop is inside or outside a droplist. The library set's a wrong value to the flag when trying to place the tile as the last element of the row.

The changes are in @flogo-web/lib-client/diagram and @flogo-web/plugins/stream-client.

How has this been tested?

Manally tested the flows and stream designer page with following scenarios:

• [x] Drag an item and drop it anywhere except last tile in the same row
• [x] Drag an item and drop it anywhere except last tile in any other row
• [x] Drag an item and drop it as a last time in the same row
• [x] Drag an item and drop it as a last time in a different row
• [x] Drag an item and drop it in empty place

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build/CI related changes
• [ ] Documentation related changes
• [ ] Other... Please describe:

Checklist:

• [X] My code follows the code style of this project.
• [X] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.