chore: remove Node 8 references and some dead code (#9284)

* chore: remove Node 8 references and some dead code

* import async hooks normally

* bump node to 8.3 because V8 6.0 with Turbofan and better perf

* update comments in pretty-format

Author: thymikee

docs/CLI.md

@@ -158,7 +158,7 @@ Print debugging info about your Jest config.
 
 ### `--detectOpenHandles`
 
-Attempt to collect and print open handles preventing Jest from exiting cleanly. Use this in cases where you need to use `--forceExit` in order for Jest to exit to potentially track down the reason. This implies `--runInBand`, making tests run serially. Implemented using [`async_hooks`](https://nodejs.org/api/async_hooks.html), so it only works in Node 8 and newer. This option has a significant performance penalty and should only be used for debugging.
+Attempt to collect and print open handles preventing Jest from exiting cleanly. Use this in cases where you need to use `--forceExit` in order for Jest to exit to potentially track down the reason. This implies `--runInBand`, making tests run serially. Implemented using [`async_hooks`](https://nodejs.org/api/async_hooks.html). This option has a significant performance penalty and should only be used for debugging.
 
 ### `--env=<environment>`
 

jest.config.ci.js

@@ -7,8 +7,8 @@
 
 'use strict';
 
-// Object spread is just node 8
-module.exports = Object.assign({}, require('./jest.config'), {
+module.exports = {
+  ...require('./jest.config'),
   coverageReporters: ['json'],
   reporters: [
     [
@@ -17,4 +17,4 @@ module.exports = Object.assign({}, require('./jest.config'), {
     ],
     ['jest-silent-reporter', {useDots: true}],
   ],
-});
+};

package.json

@@ -144,6 +144,6 @@
     "logo": "https://opencollective.com/jest/logo.txt"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   }
 }

packages/babel-jest/package.json

@@ -26,7 +26,7 @@
     "@babel/core": "^7.0.0"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "publishConfig": {
     "access": "public"

packages/babel-plugin-jest-hoist/package.json

@@ -7,7 +7,7 @@
     "directory": "packages/babel-plugin-jest-hoist"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "license": "MIT",
   "main": "build/index.js",

packages/babel-preset-jest/package.json

@@ -17,7 +17,7 @@
     "@babel/core": "^7.0.0"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "publishConfig": {
     "access": "public"

packages/diff-sequences/package.json

@@ -16,7 +16,7 @@
     "diff"
   ],
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "main": "build/index.js",
   "types": "build/index.d.ts",

packages/eslint-config-fb-strict/package.json

@@ -20,7 +20,7 @@
     "eslint-plugin-react": "^7.1.0"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "publishConfig": {
     "access": "public"

packages/expect/package.json

@@ -22,7 +22,7 @@
     "immutable": "^4.0.0-rc.12"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "publishConfig": {
     "access": "public"

packages/jest-changed-files/package.json

@@ -15,7 +15,7 @@
     "throat": "^5.0.0"
   },
   "engines": {
-    "node": ">= 8"
+    "node": ">= 8.3"
   },
   "publishConfig": {
     "access": "public"