[slow sign in] Fetch generic password only once

Previously it was fetched each time when any realm db was opened,
but it should happen only once. Saves up to 300ms on sign in.

src/status_im/utils/keychain/core.cljs

@@ -129,14 +129,23 @@
   (comp validate
         string->js-array))
 
+(defonce generic-password (atom nil))
+
 (defn get-encryption-key []
-  (log/debug "initializing realm encryption key...")
+  (log/debug "PERF" "initializing realm encryption key..." (.now js/Date))
-  (.. (.getGenericPassword rn/keychain)
+  (if @generic-password
-      (then
+    (js/Promise.
-       (fn [res]
+     (fn [on-success _]
-         (if res
+       (on-success (security/unmask @generic-password))))
-           (handle-found res)
+    (.. (.getGenericPassword rn/keychain)
-           (handle-not-found))))))
+        (then
+         (fn [res]
+           (if res
+             (let [handled-res (handle-found res)]
+               (reset! generic-password
+                       (security/->MaskedData handled-res))
+               handled-res)
+             (handle-not-found)))))))
 
 (defn safe-get-encryption-key
   "Return encryption key or empty string in case invalid/empty"

test/cljs/status_im/test/utils/keychain/core.cljs

@@ -40,7 +40,8 @@
 (deftest key-is-weak
   (async
    done
-   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password (key->json weak-key)}))}]
+   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password (key->json weak-key)}))}
+                 keychain/generic-password (atom nil)]
      (testing "it returns a valid key"
        (.. (keychain/get-encryption-key)
            (then (fn [_]
@@ -54,7 +55,8 @@
 (deftest safe-key-is-not-valid
   (async
    done
-   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password (key->json weak-key)}))}]
+   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password (key->json weak-key)}))}
+                 keychain/generic-password (atom nil)]
      (testing "it returns a valid key"
        (.. (keychain/safe-get-encryption-key)
            (then (fn [k]
@@ -67,7 +69,8 @@
 (deftest safe-key-is-nil
   (async
    done
-   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password nil}))}]
+   (with-redefs [rn/keychain #js {:getGenericPassword (constantly (.resolve js/Promise #js {:password nil}))}
+                 keychain/generic-password (atom nil)]
      (testing "it returns a valid key"
        (.. (keychain/safe-get-encryption-key)
            (then (fn [k]