Issues with multi-monitor support - incorrect detection, not remembering selected scheme

**Describe the bug**
When a second monitor is connected when the OS is already started, the names show "Monitor 1" and "Monitor 2" instead of the monitor names.
Moreover, "Monitor 1" seems to always correspond to the default monitor. However, in the system the newly connected monitor might be assigned as default - in such case the tiling mapping, which presumes "Monitor 1" being the original single monitor, will not be correct anymore.
This doesn't happen if the system is booted with 2 monitors attached - in such case it would continue recognizing the right names and perform the right assignments to the monitors.

And in case the monitor is disconnected and connected again, the default tiling mapping corresponding to the monitor changes - which is also super-annoying. When disconnecting the work laptop and taking it home, and then coming back and reconnecting it - the tiling scheme for the external monitor needs to be chosen again.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

**Screenshots**
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**Information (please complete the following):**
- Tiling Shell version: [e.g. v9.0]
- GNOME version: [e.g. 42, 46]. If you don't know, run `gnome-shell --version`

**Additional context**
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