Prevent selection ranges to intersect once the model structure changes

[Reinmar]

📝 Provide a description of the improvement

Visible in RemoveRowCommand's tests when you delete the fragment which prevents this error:

        ✖ should properly remove row if reversed selection is made
          Chrome 80.0.3987 (Mac OS X 10.15.2)
        CKEditorError: model-selection-range-intersects: Trying to add a range that intersects with another range in the selection. Read more: https://ckeditor.com/docs/ckeditor5/latest/framework/guides/support/error-codes.html#error-model-selection-range-intersects
         {"addedRange":{"start":{"root":"main","path":[0,0,0],"stickiness":"toNext"},"end":{"root":"main","path":[0,0,1],"stickiness":"toPrevious"}},"intersectingRange":{"start":{"root":"main","path":[0,0,0],"stickiness":"toNext"},"end":{"root":"main","path":[0,0,1],"stickiness":"toPrevious"}}}
            at LiveSelection._checkRange (webpack:///./packages/ckeditor5-engine/src/model/selection.js?:767:11)
            at LiveSelection._prepareRange (webpack:///./packages/ckeditor5-engine/src/model/documentselection.js?:832:8)
            at LiveSelection._fixGraveyardSelection (webpack:///./packages/ckeditor5-engine/src/model/documentselection.js?:1154:26)
            at Model.LiveSelection.listenTo.priority (webpack:///./packages/ckeditor5-engine/src/model/documentselection.js?:646:10)
            at Model.fire (webpack:///./packages/ckeditor5-utils/src/emittermixin.js?:218:30)
            at Model.<computed> [as applyOperation] (webpack:///./packages/ckeditor5-utils/src/observablemixin.js?:263:16)
            at applyRemoveOperation (webpack:///./packages/ckeditor5-engine/src/model/writer.js?:1564:8)
            at Writer.remove (webpack:///./packages/ckeditor5-engine/src/model/writer.js?:549:4)
            at RemoveRowCommand._removeRow (webpack:///./packages/ckeditor5-table/src/commands/removerowcommand.js?:140:10)
            at Object.eval [as callback] (webpack:///./packages/ckeditor5-table/src/commands/removerowcommand.js?:81:10)

This is due to rows being removed and ranges from the selection falling into one place.

May be related to #3504. @scofalik may be proud of himself for foreseeing this.

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[Reinmar]

May also resolve #6382.