[Bug]: Multiple Source Media Reps not consistent when reopening session

### What happened?

we are using the multiple source media reps and everything works fine while we are running the session.

however problems arise whe nwe save a session and want to reopen it again.

Somehow the source nodes loose the connection to the switch node and to each other.

These commands don't work anymore on the soruce nodes:
- commands.sourceMediaRepsAndNodes
-> only gives the same node and repname it was started from
-> solution: run with the switch node as the argument (then we get all reps and nodes)
- commands.sourceMediaRepSwitchNode
-> doesn't work on any source node after session reopen
- commands.sourceMediaRepSourceNode
-> doesn't work on any soruce node after session reopen

Our solution is saving the sourceMediaRepSourceNode on every other represantion as a property and then only checking this property instead of using commands.sourceMediaRepSourceNode
and saving the switch node on the sourceNode so we can use commands.sourceMediaRepsAndNodes properly

steps to reproduce:
1. add a source media rep to a source
2. save the session
3. open the sessio again
4. try the different functions on the source nodes

### List all the operating systems versions where this is happening

linux

### On what computer hardware is this happening?

any

### Relevant console log output

```shell

```

### Environment variables

_No response_

### Extra information

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Reproduce the session save and reopen steps, then inspect the source-node entry points commands.sourceMediaRepsAndNodes, commands.sourceMediaRepSwitchNode, and commands.sourceMediaRepSourceNode. Compare their behavior before and after reopening; done means source nodes retain their switch and source-node connections and all three commands work again after reload.

Written by the indexing model from the issue text.