Upgrades older Tapable.plugin methods to new hook/tap methods

[drolsen]

Webpack 4 has moved away from Tapable.plugin methods for new API hook/tap methods.

• https://webpack.js.org/api/plugins/#tapable
• https://webpack.js.org/api/compiler-hooks/#compilation
• https://webpack.js.org/api/compiler-hooks/#normalmodulefactory
• https://webpack.js.org/api/compiler-hooks/#emit

Please note, this moves the normalModuleFactory usage outside of the compiler.hooks.compilation tap due to scope change during API abstraction that leads to normalModuleFactory indexOf to never find a match unless re-scoped to the root of apply.

#171
webpack/webpack#6568

Thanks!