Move SDC Component namespace to Core namespace

We, the mentoring team, are triaging issues for first time contributors at DrupalCon Lille and I think this is a good issue for the contribution day.
We are reserving this issue so please don't work on this issue if you are not at DrupalCon Lille. You can continue the work when the event is over.

The example issue that can be followed:
📌 Move isRenderArray from SDC to Drupal\Core\Render\Element Fixed

I'll be working on this issue with @simonTrivali, @shriaas and @MathiasBaetens

This one should be postponed on 📌 Move SDC *.schema.json to Core namespace Active

Merged onto the feature branch! Thanks @plopesc!

Setting to Active after the blocker was fixed.

Created MR: https://git.drupalcode.org/issue/drupal-3352256/-/merge_requests/2

I left some optional minor suggestions.

There was some discussion in the MR. After this I merged the changes to the bigger MR.

Automatically closed - issue fixed for 2 weeks with no activity.