Implement workaround for NavigationAgent avoidance with RollbackSynchronizer

[MunWolf]

✨ Description

When you enable avoidance on NavigationAgents you need to wait for the NavMap step function (which signals velocity_computed).
This usually happens once every physics_process which means you can't use avoidance with rollback.
Not exactly sure what is the best way to fix it since it is avoidance is tightly coupled with the NavigationServer

Use case

Allows the use of navigation agent avoidance during rollback.

Distribution

Probably should live in netfox.extras as it is a similar problem to the physics server

[albertok]

NavigationAgents should run on regular ticks.

If they are in the rollback loop it means they are going back in time and altering history.