Move app/src (mostly) to flipper-ui-core/src

Summary:
This diff moves all UI code from app/src to app/flipper-ui-core. That is now slightly too much (e.g. node deps are not removed yet), but from here it should be easier to move things out again, as I don't want this diff to be open for too long to avoid too much merge conflicts.

* But at least flipper-ui-core is Electron free :)
* Killed all cross module imports as well, as they where now even more in the way
* Some unit test needed some changes, most not too big (but emotion hashes got renumbered in the snapshots, feel free to ignore that)
* Found some files that were actually meaningless (tsconfig in plugins, WatchTools files, that start generating compile errors, removed those

Follow up work:
* make flipper-ui-core configurable, and wire up flipper-server-core in Electron instead of here
* remove node deps (aigoncharov)
* figure out correct place to load GKs, plugins, make intern requests etc., and move to the correct module
* clean up deps

Reviewed By: aigoncharov

Differential Revision: D32427722

fbshipit-source-id: 14fe92e1ceb15b9dcf7bece367c8ab92df927a70

desktop/flipper-ui-core/src/utils/pathUtils.tsx

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+// We use sync access once per startup.
+/* eslint-disable node/no-sync */
+
+import path from 'path';
+import fs from 'fs';
+
+import config from '../fb-stubs/config';
+import {getRenderHostInstance} from '../RenderHost';
+
+export function getStaticPath(
+  relativePath: string = '.',
+  {asarUnpacked}: {asarUnpacked: boolean} = {asarUnpacked: false},
+) {
+  const staticDir = getRenderHostInstance().paths.staticPath;
+  const absolutePath = path.resolve(staticDir, relativePath);
+  // Unfortunately, path.resolve, fs.pathExists, fs.read etc do not automatically work with asarUnpacked files.
+  // All these functions still look for files in "app.asar" even if they are unpacked.
+  // Looks like automatic resolving for asarUnpacked files only work for "child_process" module.
+  // So we're using a hack here to actually look to "app.asar.unpacked" dir instead of app.asar package.
+  return asarUnpacked
+    ? absolutePath.replace('app.asar', 'app.asar.unpacked')
+    : absolutePath;
+}
+
+export function getChangelogPath() {
+  const changelogPath = getStaticPath(config.isFBBuild ? 'facebook' : '.');
+  if (fs.existsSync(changelogPath)) {
+    return changelogPath;
+  } else {
+    throw new Error('Changelog path path does not exist: ' + changelogPath);
+  }
+}