Move all dialog buttons to the right and fix their order

Fixes https://github.com/vector-im/riot-web/issues/5689

Some dialogs had their own CSS that prevented the buttons from being placed in the right spot. This has been fixed by using a generic standard for the buttons. The only strange dialog that needed more CSS was the devtools dialog due to the header.

Not all dialogs have been checked - I spot-checked about half of them and verified the CSS manually on an established account. It's hard to get at all the dialogs without convoluted testing.

res/css/views/dialogs/_DevtoolsDialog.scss

@@ -14,6 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+.mx_DevTools_dialog {
+    padding-right: 58px;
+}
+
 .mx_DevTools_content {
     margin: 10px 0;
 }