[PP1] Add eventListener to Menu title when toolbar is collapsed

This one is more complicated than just merging it in because it's changing a behavior tested on the users and that worked.

I assume you are adding this because you are missing the link to the top level pages, which is a discussion we had when creating the existing implementation: the "dropdowns" didn't work because were generating confusion and thy aren't a common pattern. It meant removing the link to the top pages to convert them into a behavior close to "toggles"/details.

The discussion that followed was: "which value do these pages give and what will we be loosing if we remove them (initially just the ability to access the from the navigation)?" The highlights were:

• The only extra they bring up now is the description
• The only one that might feel necessary to some users is only the "Configuration" one
• If the feedback is that user really need them, we could add a "see all" as a first or last item in the list.
• We assumed on previous discussions, and was discussed again here, that we need consistency between submenus in opened/collapsed states (items and behavior)

Given the context (I hope I haven't missed anything), adding a "link" when the toolbar is collapsed vs when it is not might be confusing. But since that is an assumption and can be wrong, I'd say let's add it to the things to test at DrupalCon EU since it's around the corner: 📌 Toolbar Prototype Usability Testing Phase 3 Fixed and we make sure we can decide base on data.

Also, I'm sure you're adding this for a reason, so if you've got feedback from users or it's an assumption you're making it would be really helpful to have it documented. Thanks @saschaeggi!!

There was a big rebase, so i had conflicts per each file added by @saschaeggi in the merge request. I decided just to make git rebase --skip and restore changes quickly (since there was few changes). But now in the list of commiters in MR there is only me (but i think it's not an issue, correct me if i'm wrong).

Also, we had a problem with some parent menu elements, like `Shortcuts` or `User`. Initially it was just a titles with no url defined. But these items should be also clickable, so i tried to simulate url to these titles taken from the first item in child tree.

Keeping issue on "Needs review" for getting more eyes

Btw why it cannot be just link?

if menu level===0 and item has url => a href
else div

Sorry if I wasn't clear enough: this new behavior won't make it in unless user tests validate it is a need or an expected behavior.
We added as a thing to test during 📌 Toolbar Prototype Usability Testing Phase 3 Fixed but we finally weren't able to focus on things beyond the mobile. So postponing this until we have an answer from 📌 Toolbar Prototype Usability Testing Phase 4 Active so there are not more efforts invested here.
To mention also that during DrupaCon several people agreed on being confusing having different behavior from collapsed to opened sidebar.

Closing this, as the new designs, with the drawer, does incorporate links on the menu titles.