Eliminate remaining Electron 8 deprecations

* Change systemPreferences.isDarkMode() to nativeTheme.shouldUseDarkColors

* Remove vibrancy parameter to BrowserWindow

* Update curve25519-n; removes context-aware deprecation warning

* Set app.allowRendererProcessReuse = true to remove warning

* Move from deprecated setters to direct property set

* Serialized sender certificates: Store less, store plain object

* isMenuBarAutoHide -> autoHideMenuBar

* UUID: Fix sealed sender indicator on message details screen

* Data._cleanData: Remove function keys, handle null in array

Also:
- run _cleanData when saving attachment download jobs
- remove job from jobs table when the send itself throws error

* _cleanData: Don't dig into strings, booleans, or numbers

* getPropsForMessageDetail: Make it clear what we're reducing

Co-authored-by: Ken Powers <ken@signal.org>

preload.js

@@ -13,7 +13,7 @@ try {
 
   const { remote } = electron;
   const { app } = remote;
-  const { systemPreferences } = remote.require('electron');
+  const { nativeTheme } = remote.require('electron');
 
   window.PROTO_ROOT = 'protos';
   const config = require('url').parse(window.location.toString(), true).query;
@@ -38,22 +38,16 @@ try {
   window.isBehindProxy = () => Boolean(config.proxyUrl);
 
   function setSystemTheme() {
-    window.systemTheme = systemPreferences.isDarkMode() ? 'dark' : 'light';
+    window.systemTheme = nativeTheme.shouldUseDarkColors ? 'dark' : 'light';
   }
 
   setSystemTheme();
 
   window.subscribeToSystemThemeChange = fn => {
-    if (!systemPreferences.subscribeNotification) {
-      return;
-    }
-    systemPreferences.subscribeNotification(
-      'AppleInterfaceThemeChangedNotification',
-      () => {
-        setSystemTheme();
-        fn();
-      }
-    );
+    nativeTheme.on('updated', () => {
+      setSystemTheme();
+      fn();
+    });
   };
 
   window.isBeforeVersion = (toCheck, baseVersion) => {