Make lodash imports tree-shakeable

Summary

With babel-plugin-lodash being removed, we need to make sure we follow the following guideline with lodash imports:

// bad
import _ from "lodash"

// bad
// babel-plugin-lodash would transform this into the `good` case during build time
import { map } from "lodash"

// good
import map from "lodash/map"

So this issue is to replace all bad cases with the good one.