Calendar event summary modal accessibility improvements

Moving a change to this issue (as a bug, so can be backported) from MDL-73938 regarding lameze' change proposed in this comment from that task

Adding the title to the url helps but only if the location is a link, if the location is a text the information still not accessible. I had discussed with the accessibility legend rezaie9 about this issue and in order to make the event summary content accessible that data should be presented as a "table" so it is accessible enough for screen reader users. We come up with this patch that improves the accessibility in the event summary modal. Inspecting the data with the fix using Chrome's accessibility too I can see that the data is now presented as a table: