Reduce number of dependencies for the product categories list block

[mikejolley]

This PR improves how JS powered blocks work on the frontend, reducing the overall number of dependencies. In testing, this reduced downloaded JS from 4.8MB to 2.2MB.

Fixes #762

The changes to the webpack config are to prevent wp.element and lodash being enqueued on the frontend - we can use React only here.

How to test the changes in this Pull Request:

1. before checking out this branch, create some product category list blocks in a page
2. checkout and build
3. confirm build/frontend.deps.js only contains ["react","react-dom","wp-i18n","wp-polyfill"]
4. check existing list blocks work in the editor and on the frontend
5. create a new product category list block - ensure it works as expected

Changelog

Reduced the number of JavaScript assets needed for the Product Category List block to improve performance.

[Aljullu]

Thanks for working on this @mikejolley, that was a big refactor and it results in much lower file sizes, good job! 👏

I added some comments below, but overall looking good. 👍

[mikejolley]

Ready for another look @Aljullu. I handled the CSS change too (wasn't difficult) and cleaned up the ID generation using a HOC. Let me know your thoughts and if you think it's good for 2.3.

[Aljullu]

Thanks for the fixes @mikejolley! Everything is working fine and code looks good. I just added one minor comment but once it's addressed this is ready to go.

[Aljullu]

I know that's very nitpicky, but what do you think about renaming withComponentID and componentID to withComponentId and componentId (notice the camel case)? This way it's consistent with withInstanceIdand instanceId.

This also seems to be the consensus they arrived in Gutenberg: WordPress/gutenberg#6741.