Integrate with Workspaces

Added quick proto here.
I tried to reuse all existing components as much as possible.

I really think it shouldn't be `workspaces only` MR. We need to create some common UI for that panel. And probably for layout builder/announcements etc panels aswell.

So I've added .toolbar-panel in temporary styles.

@ckrina please take a look! Thanks

Adding link to related issue in Workspaces #3096017: Finalize the Workspaces UI → .

@ckrina

#4: I agree we should also take a look around what things other core/contrib will want to add to this tool.
We need to keep in mind that other modules 'opt-in' to using toolbar via hook_toolbar:

• Workspaces: add a 'tab' (only) and attaches js/css via library api (which opens the top fixed off-canvux drawer)
• Acquia Connector: add a tab (only) opens to external hosting tools dashboard.
• Devel: adds 'tab' and 'tray' of child menu item [see: \Drupal\devel\ToolbarHandler]
• demo_umami: adds 'tab' item to say

^I would antipate that devel would themselves convert to a menu and be placed in within the 'admin' menu (left side). However this is reminding of the purpose of top bar: for these such of items!

Propose: Top bar also adds Layout for right/left position.
-> convert 'local tasks' to a plugin to be placed. q: Is NavigationBlock currently flexible enough to also be used this way
-> info and docs about the plugins.

DX:
->how can other modules install their items?

Moving to Needs work after getting Navigation into core.

Actually, also postponing it until we have designs for this so nobody else tries to implement something that has to be changed later.

Following as this also impacts Tour (which is now contrib)

Navigation should have a 'pill' plugin item that lets contrib/core components simply add this 'link' for this wider 'task markers'