Protos that Redefine Field Names Cause Unexpected Behavior

[CoolSpy3]

Describe the Bug
It looks like this is a bug in the handling of proto fields with the same names. My best guess is that it's maybe a result of WbNode:1740 checking for field existence by name rather than something more robust.

I did some basic debugging and it looks like, for the example below, loading the proto causes Webots to recurse indefinitely on WbNode:1305 because node == this. In essence, this means that one of the nodes is considered its own subnode. My guess is that Webots thinks SolidProto.children = Group.children, so Group is contained in Group.children.

I've also noticed a few other cases where the code assumes that field names dictate their behavior (ex. WbField:336-343). (Although this example is not likely to cause this crash.)

Steps to Reproduce

1. Create the following proto:

#VRML_SIM R2024a utf8

EXTERNPROTO "SolidProto.proto"

PROTO SolidProtoContainer [
  field MFNode children []
]
{
SolidProto {
  children [
    Group {
      children IS children
    }
  ]
}
}

(Note that this depends on the SolidProto.proto file in tests/api/protos)
2. Try to add the proto to a world
3. Webots crashes
4. Change the field name to children1 and try to load the proto again
5. Webots successfully loads the proto and does not crash.

Expected behavior
Webots should load the proto without crashing regardless of the field name.

System

• Operating System: Windows 10
• Graphics Card: NVIDIA GeForce GTX 1050 Ti