Improve event indexing status strings for translation

The strings used for the count of rooms was hard to translate, so this adds a
bit more context.

src/async-components/views/dialogs/eventindex/ManageEventIndexDialog.js

@@ -144,8 +144,10 @@ export default class ManageEventIndexDialog extends React.Component {
                 <div className='mx_SettingsTab_subsectionText'>
                     {_t("Space used:")} {formatBytes(this.state.eventIndexSize, 0)}<br />
                     {_t("Indexed messages:")} {formatCountLong(this.state.eventCount)}<br />
-                    {_t("Number of rooms:")} {formatCountLong(this.state.crawlingRoomsCount)} {_t("of ")}
-                    {formatCountLong(this.state.roomCount)}<br />
+                    {_t("Indexed rooms:")} {_t("%(crawlingRooms)s out of %(totalRooms)s", {
+                        crawlingRooms: formatCountLong(this.state.crawlingRoomsCount),
+                        totalRooms: formatCountLong(this.state.roomCount),
+                    })} <br />
                     {crawlerState}<br />
                     <Field
                         id={"crawlerSleepTimeMs"}

src/i18n/strings/en_EN.json

@@ -2094,8 +2094,8 @@
     "Riot is securely caching encrypted messages locally for them to appear in search results:": "Riot is securely caching encrypted messages locally for them to appear in search results:",
     "Space used:": "Space used:",
     "Indexed messages:": "Indexed messages:",
-    "Number of rooms:": "Number of rooms:",
-    "of ": "of ",
+    "Indexed rooms:": "Indexed rooms:",
+    "%(crawlingRooms)s out of %(totalRooms)s": "%(crawlingRooms)s out of %(totalRooms)s",
     "Message downloading sleep time(ms)": "Message downloading sleep time(ms)",
     "Failed to set direct chat tag": "Failed to set direct chat tag",
     "Failed to remove tag %(tagName)s from room": "Failed to remove tag %(tagName)s from room",