chore!: replace MLAPI namespace with Unity.Multiplayer.Netcode

[0xFA11]

part of our upcoming MLAPI rebranding, we need to change our namespaces around the codebase.

[SamuelBellomo]

I'm wondering if using "Unity.NGO" instead of "Unity.Netcode" would be better to differentiate with dots netcode.

[becksebenius-unity]

Changes LGTM assuming there's alignment on the namespace. I don't have a problem with it, although tools is using Unity.Multiplayer and we may want to change that too to follow suit (I'll follow up on this).

[becksebenius-unity]

This will need some really good messaging so internal devs all know what to expect, and any outstanding PRs know to merge backwards even if there's no conflicts.

[mattwalsh-unity]

Yeah, @becksebenius-unity I think you're right, I think we'd have to all move under Unity.Netcode

[SamuelBellomo]

Yeah, @becksebenius-unity I think you're right, I think we'd have to all move under Unity.Netcode

For Boss Room, I'd lean toward keeping with our "BossRoom" namespace, since it's all user side code. It'd make sense to not mix namespaces for this.