Move network import type from NodeInput::Network to NodeNetwork in order to enable automatic Into node insertion

Instead of annotating type for each NodeInput::network usage, the types should be annotated in a single vec for every import.
For example we do something like
```
pub fn node(input1){
subnode(input1: String)
subnode(input1: String)
etc
}
```

rather than
```
pub fn node(input1: String){
subnode(input1)
subnode(input1)
etc
}
```
Technically I dont think we even need to annotate the parameters, since their types can be resolved at compile time. However, this system would be useful/necessary for automatic into node insertion (#1890, which can also be used to solve #1919), as well as displaying what types can be connected to a node when hovering over the input.

Discussions here:
https://discord.com/channels/731730685944922173/731738914812854303/1253116397370998794
https://discord.com/channels/731730685944922173/860830913390575646/1271586374314885201
https://discord.com/channels/731730685944922173/860830913390575646/1271605307771981987

And a more recent recap asking for a reminder about what this is and its status: https://discord.com/channels/731730685944922173/1059075292414619689/1387941282701119550

Start by tracing NodeInput::Network and NodeNetwork, then review the linked discussions and related issues #1890 and #1919 to establish the intended type representation. Done means imports use a single type-annotated vector that supports automatic Into node insertion and exposes connectable types for hover information.

Vom Indexierungsmodell aus dem Issue-Text verfasst.