fix(grid): set flex shrink to 0 for all display containers

Disallow display container shrinkage to prevent inner content(cells)
from having different widths when set in fraction values (%).

Closes #3918

Author: simeonoff

projects/igniteui-angular/src/lib/core/styles/components/_common/_igx-display-container.scss

@@ -3,6 +3,7 @@
     position: relative;
     width: 100%;
     overflow: hidden;
+    flex-shrink: 0;
 }
 
 %display-container--inactive {