Extract builder queue api from gfx_showbuilderqueue.lua

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gfx_showbuilderqueue.luawas responsible for tracking active build orders and displaying their building ghosts. I want to create another widget that also needs to track build orders, so I’ve extracted that logic into api_builder_queue.lua.

The API now handles build order tracking, while gfx_showbuilderqueueis only responsible for displaying the ghosts.

The only functional change is that previously, whenever a unit’s commands changed, all of its ghosts were redrawn. Now, only obsolete ghosts are removed. From the player’s perspective, there should be no visible difference in behavior.

Test steps

• Start a match with allied AI. Make some long build queues with various constructors.
• The building ghosts should be visible for both player and allies.
• Cancel and/or modify the orders - the ghosts should update properly
• Destroy the builder in the middle of the queue - ghosts should be cleared
• Share the builder in the middle of the queue - ghosts should be still visible if builder continues the queue
• Open some 8v8 replay. You should see ghosts of both teams
• Enable Player View. You should see ghosts only of this player's team