Update webpack (#177265)

* update webpack

* update `@types/webpack`

* update copy-webpack-plugin

* update @types/webpack in build

* fix compile error in @types/eslint

build/package.json

@@ -12,7 +12,6 @@
     "@types/cssnano": "^4.0.0",
     "@types/debounce": "^1.0.0",
     "@types/debug": "4.1.5",
-    "@types/eslint": "4.16.1",
     "@types/fancy-log": "^1.3.0",
     "@types/fs-extra": "^9.0.12",
     "@types/glob": "^7.1.1",
@@ -38,7 +37,6 @@
     "@types/through2": "^2.0.36",
     "@types/tmp": "^0.2.1",
     "@types/underscore": "^1.8.9",
-    "@types/webpack": "^4.41.25",
     "@types/xml2js": "0.0.33",
     "@vscode/iconv-lite-umd": "0.7.0",
     "@vscode/vsce": "^2.16.0",