Re-introduce inactive workspaces collapsible component on the workspaces list

[gtsiolis]

Problem to solve

The new inactive workspaces grouping introduced in #10450 was reverted in #10663.

See relevant discussion (internal). Cc @AlexTugarev @geropl

Proposal

Given, this seems like a trivial fix, like the one back in #3945, let's re-introduce back this feature.

For more context, see relevant discussion (internal).

[svenefftinge]

Happy to take this, so it doesn't side-track the team too much 😇