Move the code related to plugin loading / installation to "flipper-plugin-lib"

Summary:
Sorry for so long diff, but actually there are no functional changes, just refactoring to make further changes of Plugin Manager easier to understand.

I've de-coupled the code related to plugin management from UI code and moved it from PluginInstaller UI component (which will be replaced soon by new UI) to "flipper-plugin-lib".  So pretty much everything related to plugin discovery and installation now consolidated in this package.

Additionally, this refactoring enables re-using of plugin management code in "flipper-pkg", e.g. to create CLI command for plugin installation from NPM, e.g.: `flipper-pkg install flipper-plugin-reactotron`.

Reviewed By: passy

Differential Revision: D23679346

fbshipit-source-id: 82e7b9de9afa08c508c1b228c2038b4ba423571c

desktop/app/src/utils/pluginManager.tsx

@@ -1,57 +0,0 @@
-/**
- * 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
- */
-
-import path from 'path';
-import {homedir} from 'os';
-import {PluginMap, PluginDetails} from 'flipper-plugin-lib';
-import {default as algoliasearch, SearchIndex} from 'algoliasearch';
-import NpmApi, {Package} from 'npm-api';
-import semver from 'semver';
-
-const ALGOLIA_APPLICATION_ID = 'OFCNCOG2CU';
-const ALGOLIA_API_KEY = 'f54e21fa3a2a0160595bb058179bfb1e';
-
-export const PLUGIN_DIR = path.join(homedir(), '.flipper', 'thirdparty');
-
-// TODO(T57014856): This should be private, too.
-export function provideSearchIndex(): SearchIndex {
-  const client = algoliasearch(ALGOLIA_APPLICATION_ID, ALGOLIA_API_KEY);
-  return client.initIndex('npm-search');
-}
-
-export type UpdateResult =
-  | {kind: 'up-to-date'}
-  | {kind: 'error'; error: Error}
-  | {kind: 'update-available'; version: string};
-
-export async function findPluginUpdates(
-  currentPlugins: PluginMap,
-): Promise<[string, UpdateResult][]> {
-  const npm = new NpmApi();
-
-  return Promise.all(
-    Array.from(currentPlugins.values()).map(
-      async (currentPlugin: PluginDetails): Promise<[string, UpdateResult]> =>
-        npm
-          .repo(currentPlugin.name)
-          .package()
-          .then((pkg: Package): [string, UpdateResult] => {
-            if (semver.lt(currentPlugin.version, pkg.version)) {
-              return [
-                currentPlugin.name,
-                {kind: 'update-available', version: pkg.version},
-              ];
-            } else {
-              return [currentPlugin.name, {kind: 'up-to-date'}];
-            }
-          })
-          .catch((err) => [currentPlugin.name, {kind: 'error', error: err}]),
-    ),
-  );
-}