Flatten the shared/ folder (#11297)

* shared/src -> shared

It's not a real package and doesn't even have package.json.
This will also make importing less weird if we drop Haste.

* Get rid of shared/utils

Moved event-specific into shared/event.
Moved rest to the root since distinction has always been pretty arbitrary.

* Fix references to old shared/src paths

scripts/prettier/index.js

@@ -38,6 +38,7 @@ const config = {
       'packages/*/*.js',
       // Source files
       'packages/*/src/**/*.js',
+      'packages/shared/**/*.js',
     ],
     ignore: ['**/node_modules/**'],
   },

scripts/release/build-commands/update-package-versions.js

@@ -20,7 +20,7 @@ const update = async ({cwd, dry, version}) => {
     await writeJson(packagePath, rootPackage, {spaces: 2});
 
     // Update ReactVersion source file
-    const reactVersionPath = join(cwd, 'packages/shared/src/ReactVersion.js');
+    const reactVersionPath = join(cwd, 'packages/shared/ReactVersion.js');
     const reactVersion = readFileSync(reactVersionPath, 'utf8').replace(
       /module\.exports = '[^']+';/,
       `module.exports = '${version}';`

scripts/rollup/modules.js

@@ -189,9 +189,7 @@ function getInternalModules(moduleType) {
   // we tell Rollup where these files are located internally, otherwise
   // it doesn't pick them up and assumes they're external
   let aliases = {
-    reactProdInvariant: resolve(
-      './packages/shared/src/utils/reactProdInvariant.js'
-    ),
+    reactProdInvariant: resolve('./packages/shared/reactProdInvariant.js'),
   };
   if (moduleType === RENDERER) {
     // Renderers bundle the whole reconciler.

scripts/tasks/version-check.js

@@ -15,7 +15,7 @@ const versions = {
     .version,
   'packages/react-test-renderer/package.json': require('../../packages/react-test-renderer/package.json')
     .version,
-  'packages/shared/src/ReactVersion.js': require('../../packages/shared/src/ReactVersion'),
+  'packages/shared/ReactVersion.js': require('../../packages/shared/ReactVersion'),
 };
 
 let allVersionsMatch = true;