ARIA Accessibility improvements (#10675)

* Fix confusing tab indexes in EventTilePreview

* Stop using headings inside buttons

* Prefer labelledby and describedby over duplicated aria-labels

* Improve semantics of tables used in settings

* Fix types

* Update tests

* Fix timestamps

res/css/views/settings/_CrossSigningPanel.pcss

@@ -17,7 +17,12 @@ limitations under the License.
 .mx_CrossSigningPanel_statusList {
     border-spacing: 0;
 
-    td {
+    th {
+        text-align: start;
+    }
+
+    td,
+    th {
         padding: 0;
 
         &:first-of-type {

res/css/views/settings/_CryptographyPanel.pcss

@@ -1,3 +1,19 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 .mx_CryptographyPanel_sessionInfo {
     padding: 0em;
     border-spacing: 0px;
@@ -5,13 +21,15 @@
 .mx_CryptographyPanel_sessionInfo > tr {
     vertical-align: baseline;
     padding: 0em;
-}
 
-.mx_CryptographyPanel_sessionInfo > tr > td {
-    padding-bottom: 0em;
-    padding-left: 0em;
-    padding-right: 1em;
-    padding-top: 0em;
+    th {
+        text-align: start;
+    }
+
+    td,
+    th {
+        padding: 0 1em 0 0;
+    }
 }
 
 .mx_CryptographyPanel_importExportButtons .mx_AccessibleButton {

res/css/views/settings/_SecureBackupPanel.pcss

@@ -50,7 +50,12 @@ limitations under the License.
 .mx_SecureBackupPanel_statusList {
     border-spacing: 0;
 
-    td {
+    th {
+        text-align: start;
+    }
+
+    td,
+    th {
         padding: 0;
 
         &:first-of-type {