Map fixes to hold it together until a comprehensive rework.

Slayer: made the Overshield in Copper Top standalone.
Slayer: changed the Gauss Warthog to a standard Warthog.

- Added barriers around the top of the map.

- Removed outward-facing spawns from the crosswalks.

- Flattened the yellow pylons in Copper Top to allow vehicle passage.
- Removed some cover elements from the alleys.

These changes are temporary fixes. When the new sand canvas is released, Firebase Tononoka will be completely rebuilt to better match its original design goals and resolve several issues inherent to the current design.