Push clientside transform GridUids to children

[Tayrtahn]

When an entity is parented to another entity that does not currently exist on the client (such as when the new parent is outside of the client's PVS), the child entity does not have its GridUid set properly. This can cause issues with other systems that rely on the GridUid.

For example, when using the Follow button from the ghost roles panel, if the target entity is outside of PVS, the camera will be left at a strange rotation until the user moves:

This will also happen when parenting to a newly-created entity (see space-wizards/space-station-14#33878 (comment))

To fix this, a handler for ComponentStartup is added to the clientside TransformSystem, which calls SetGridId on any children of the parent. SetGridId handles recursing through children-of-children and aborting in the case of uninitialized transforms.

[ElectroJr]

While it does fix the specific issue with ghost following, I think this might still cause unexpected problems elsewhere. Entity/component initialization is a convoluted mess, and many components blindly expect things like TransformComponent to have already been properly set up by the time they do their startup, which might be before the transform starts up and the fix that this PR adds is applied.
Edit: I forgot that transform is given special treatment and is actually meant to always start first, but either way its probably still better to fix it some other way

I think a better / more general fix would be to change the entity state application so that it makes sure that you never have an initialized entity getting attached to a pre-init entity. I.e., the client side entity creation logic should be more like the map-loading logic, where parents are always initialized & started before their children. I'm going to start working on a PR that tries to do that instead.

[Tayrtahn]

Superseded by #5595