Disallow all anonymous default export, aside from CSF and migrations (#8535)

CSF = Storybook’s Component Story Format (CSF)

See https://storybook.js.org/docs/formats/component-story-format/

Note that the migrations still use CommonJS require, so the default export as
an object is quite ergonomic (& I don't want to touch the migrations).

.eslintrc.js

@@ -50,7 +50,7 @@ module.exports = {
     'import/newline-after-import': 'error',
     'import/no-absolute-path': 'error',
     'import/no-amd': 'error',
-    'import/no-anonymous-default-export': ['error', { 'allowObject': true }],
+    'import/no-anonymous-default-export': 'error',
     'import/no-duplicates': 'error',
     'import/no-dynamic-require': 'error',
     'import/no-mutable-exports': 'error',
@@ -92,6 +92,16 @@ module.exports = {
     'mocha/no-setup-in-describe': 'off',
   },
 
+  overrides: [{
+    files: [
+      'app/scripts/migrations/*.js',
+      '*.stories.js',
+    ],
+    rules: {
+      'import/no-anonymous-default-export': ['error', { 'allowObject': true }],
+    },
+  }],
+
   settings: {
     'react': {
       'version': 'detect',

test/lib/mock-encryptor.js

@@ -2,7 +2,7 @@ const mockHex = '0xabcdef0123456789'
 const mockKey = Buffer.alloc(32)
 let cacheVal
 
-export default {
+const mockEncryptor = {
 
   encrypt (_, dataObj) {
     cacheVal = dataObj
@@ -34,3 +34,5 @@ export default {
   },
 
 }
+
+export default mockEncryptor

ui/app/selectors/tests/send-selectors-test-data.js

@@ -1,4 +1,4 @@
-export default {
+const state = {
   'metamask': {
     'isInitialized': true,
     'isUnlocked': true,
@@ -218,3 +218,5 @@ export default {
     'errors': { 'someError': null },
   },
 }
+
+export default state