Remove `webpack` from runtime dependencies

[axetroy]

https://github.com/search?q=repo%3Avuejs%2Fvue-loader%20require(%27webpack&type=code

I found that the plugin has a runtime dependency on webpack.

As rspack matures, this is a barrier to migration.

We should remove the runtime dependency on webpack

We can get the webpack's Plugin via compiler instead of require('webpack'), which is compatible with webpack-like bundler(eg. rspack)