[Meta] Incorporate navigation side-panel in SharedUX nav component, migrate Security Solution to shared components

[tsullivan]

This is a meta issue to track progress of a plan to:

1. We'll start porting the Security navigation to the SharedUX components currently in main (prior to Project Side Navigation: Use EuiCollapsibleNavBeta component #164910).

2. We'll finish work on Project Side Navigation: Use EuiCollapsibleNavBeta component #164910. Work from Step 1 can be rebased on top

3. Work to extend the components API to support a “panel” to be displayed next to the current side nav. On mobile, that panel will not render and we rely on the landing page.

4. The first version of the “panel” API as supported from SharedUX will render content provided by the consumer.

Phase 2:
SharedUX add internal support to panel content, allowing consumers to not have to provide their own panel content to render in the panel.

[tsullivan]

Oops! It looks like we don't need this issue after all?

cc @petrklapka

[tsullivan]

Duplicate of #166883