fix: respect participant permissions for hardware access

[Antreesy]

☑️ Resolves

• Fix 'hardware cam light on in call with no camera permissions'
  • useDevices has 2-3 subscribers during the call:
    • audio control button
    • video control button
    • device preview dialog
• If user has no permissions to enable mic / camera during the call (e.g. in webinar), then MediaDeviceManager should not try to get media devices for audio / video
• refactor previous logic with subscribersCount, where we only respect existing of subscribers, but not what they requesting.
  • internal logic for composable, no reactivity needed
• in theory - should not block using devices by other apps at the same time

AI (if applicable)

• The content of this PR was partly or fully generated using AI

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After
Light on	Light off

🚧 Tasks

• ...

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[Antreesy]

/backport to stable33

[DorraJaouad]

Also Tested ✅

[nickvergessen]

I think we did this so granting permissions afterwards does not lead to a disconnect which then prompts the device picker with permissions request during the call, but up front already 🙈

But I think that is a "edge case" from our company call setup

[Antreesy]

I think we did this so granting permissions afterwards does not lead to a disconnect which then prompts the device picker with permissions request during the call

There is still a device picker working in background and before call, so general media-permission fo browser should be granted by then. During the call, it's more about holding the device (for no reasons, if there are no permissions).
From the tests, it was resolved correctly, keeping the mic/camera off