Enforce Prettier defaults + also format .babelrc and .json (#7499)

* .prettierrc: full configuration for Prettier

This way, contributors using different-from-default settings will still
use the correct prettier settings

* Makefile: also lint .babelrc.js

* Makefile: also prettify .json files

* Exclude package.json files and correct build dir

* Add more default options to prettierrc and load it in cli

This avoids prettier looking up the config for each file

* Format json

* Update prettier and eslint and reformat codebase

* Remove obsolete file

* Add comment

.prettierrc

@@ -1,5 +1,14 @@
 {
+  "arrowParens": "avoid",
   "trailingComma": "es5",
+  "useTabs": false,
+  "semi": true,
+  "singleQuote": false,
+  "bracketSpacing": true,
+  "jsxBracketSameLine": false,
+  "tabWidth": 2,
+  "parser": "babylon",
+  "printWidth": 80,
   "overrides": [{
     "files": [
       "**/codemods/*/src/**/*.js",