Move less frequently used organization pages under the org selector

[gtsiolis]

Problem to solve

Following up from #16164 (comment) and #16046 (comment), currently org navigation contains all org pages. Cc @svenefftinge

Although this was ok as for this iteration, this is causing:

1. The navigation to become more crowded.
2. The header navigation to include duplicate links for settings, linking to org settings and project settings, etc.
3. Inconsistent menu for org owners or org members, as not everyone has access to Usage or Settings.
4. Less frequently used pages like Usage, Members, and Settings are now always present to users.

Cc @selfcontained because #16164 (review).

Proposal

Move less frequently used organization pages under the org selector.

Designs

TBD (To be discussed)

In the meantime, here's an early draft how this could look like the following. Keeping only the essential menu items up there could also give room for some cool experiments, like the following layout, making the product org-centric.

Early design for a better org selector	Navigation experiment