Coroutine uploading

[Bagellll]

Today I learned 2 things.

1. Do not convert a navmesh of gm_bigcity.
2. When there are 10k+ nodes in a mesh, the net channel just dies trying to send it.

I was actually surprised that this works but it does actually prevent the (what I would consider edge case) bug where your mesh is too big, even for the last fix I did. Thanks again in advance.