Stop publishing jest/preprocessor.js to npm

Summary:
Changelog:
[Breaking][General] Remove jest/preprocessor from the react-native package

Using `react-native/jest/preprocessor` outside of the React Native repo has been deprecated since D34820086 (c1e9aa9). Here, we make this file private and stop publishing it to npm.

The supported method of using Jest in React Native projects is using the [Jest preset](https://jestjs.io/docs/tutorial-react-native) shipped as part of the `react-native` package.

NOTE: We could probably make some of the other files under `jest/` private as well, but we should go through a separate deprecation cycle with those, in case they are also being used externally by some projects. I'm leaving that for future followup at the moment.

Reviewed By: GijsWeterings

Differential Revision: D36132939

fbshipit-source-id: 300ffa6cf16232573cd3a79a34c14daaafd7aa43

jest.config.js

@@ -13,7 +13,7 @@ module.exports = {
   transform: {
     '^.+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$':
       '<rootDir>/jest/assetFileTransformer.js',
-    '.*': './jest/preprocessor_DO_NOT_USE.js',
+    '.*': './jest/private/preprocessor.js',
   },
   setupFiles: ['./jest/setup.js'],
   timers: 'fake',

package.json

@@ -14,9 +14,6 @@
     "outputName": "js-test-results.xml"
   },
   "files": [
-    "!template/node_modules",
-    "!template/package-lock.json",
-    "!template/yarn.lock",
     "android",
     "cli.js",
     "flow",
@@ -25,6 +22,7 @@
     "interface.js",
     "jest-preset.js",
     "jest",
+    "!jest/private",
     "Libraries",
     "LICENSE",
     "local-cli",
@@ -60,6 +58,9 @@
     "sdks/hermes-engine.podspec",
     "template.config.js",
     "template",
+    "!template/node_modules",
+    "!template/package-lock.json",
+    "!template/yarn.lock",
     "third-party-podspecs"
   ],
   "scripts": {