Ability to show implicit people in spaces in "DM" tab when in a space

### Your use case

#### What would you like to do? + Why would you like to do it?
This is my use case: I am in public, private (invite-only), and personal (only me) spaces. These are partially nested. I use them to organize my rooms and DMs. I also have favourites in some spaces.

Navigating to the DM tab within a space, I expect that tab to show me the DMs of that space. For me, that also includes space members. I find it highly unintuitive that the "people" tab doesn't include all people in the space and I need to navigate around more. I believe this is the same reason you chose to include "everything" in the home view: less fiddling with menus on mobile. I would like to avoid having to manage that additionally when I could just flip a switch.

#### How would you like to achieve it?
SchildiChat has that in the settings. You can probably just backport that. Imo it should default to enabled.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_