Layout v2 component

[andresmgot]

Description of the change

The Layout is the first self-written component that we render. I am following the same approach than in #1814 to conditionally load one file or another depending on the UI in the configuration. Note that the requisites to do this are:

• The component should have a container. This is needed to pass the featureFlags as a property. Most of our components already have this but it was not the case for the Layout component.
• The index file of the component will decide which of the two versions it should load.
• A second file (I've chosen to use the notation .v2) should be loaded for the Clarity UI.

Result:

With the hex UI:

With the clarity UI:

Note that the Layout component is just a wrapper, we still need to work in all the components of the different views.

Applicable issues

• ref Update Kubeapps styles/classes to use clarity.design #1354

Additional information

The change of base branch messed a bit the git history but I've also moved the UISelector to the layout component, I believe there is a better place rather than in the Header component.

[absoludity]

See inline comments. I think it'd be worth waiting for the package updates so we no longer need to wrap components in containers to access state.

[absoludity]

Note: you might to wait or my branch updating our redux/react-router dependencies etc. as you'll no longer need a container to access state (as it can be accessed via hooks). Similarly, updating connected-react-router forces adding the router state to the IStoreState as you've done manually here (ie. it'll already be done in my branch).

[andresmgot]

I prefer to merge this before so I don't have conflicts since it's quite simple, in any case, the route thing is not needed.