Clarify when memory stores are being used

This adds logging for the cases where memory only stores are being used. It also
reorganises the sync store path to match the crypto store.

Part of https://github.com/vector-im/riot-web/issues/9309

src/utils/StorageManager.js

@@ -62,15 +62,9 @@ export async function checkConsistency() {
     }
 
     if (indexedDB && localStorage) {
-        try {
+        const results = await checkSyncStore();
-            const dataInSyncStore = await Matrix.IndexedDBStore.exists(
+        if (!results.healthy) {
-                indexedDB, SYNC_STORE_NAME,
-            );
-            log(`Sync store contains data? ${dataInSyncStore}`);
-        } catch (e) {
             healthy = false;
-            error("Sync store inaccessible", e);
-            track("Sync store inaccessible");
         }
     } else {
         healthy = false;
@@ -108,6 +102,22 @@ export async function checkConsistency() {
     }
 }
 
+async function checkSyncStore() {
+    let exists = false;
+    try {
+        exists = await Matrix.IndexedDBStore.exists(
+            indexedDB, SYNC_STORE_NAME,
+        );
+        log(`Sync store using IndexedDB contains data? ${exists}`);
+        return { exists, healthy: true };
+    } catch (e) {
+        error("Sync store using IndexedDB inaccessible", e);
+        track("Sync store using IndexedDB inaccessible");
+    }
+    log("Sync store using memory only");
+    return { exists, healthy: false };
+}
+
 async function checkCryptoStore() {
     let exists = false;
     try {
@@ -128,5 +138,6 @@ async function checkCryptoStore() {
         error("Crypto store using local storage inaccessible", e);
         track("Crypto store using local storage inaccessible");
     }
+    log("Crypto store using memory only");
     return { exists, healthy: false };
 }