Change some units (Reaper grenade) to effects

[BurnySc2]

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• [x] Reaper grenade should be an effect and not a structure
• [x] Parasitc bomb (after the unit has died, the effect still lives on as a unit) should be an effect
• [x] Force field should be an effect not a unit

This can probably be achieved here https://github.com/BurnySc2/python-sc2/blob/9caa5151e04ea3107d29475949d230f52e44efac/sc2/bot_ai.py#L835 by removing them from units and adding them to self.state.effects

• [ ] Fix ravager bile effect While we are at it, the ravager bile is removed from the API too early before the bile has landed on the destination. Units will no longer try to dodge this and will probably take damage. This might need to be stored for a couple frames, or should this be handled bot specifically?
• [ ] Tactical Nuke probably has the same problem

[tweakimp]

Completed first three tasks in https://github.com/BurnySc2/python-sc2/commit/034b71af3828914d83dc10c45e9da97fa4517e0e

[tweakimp]

Added Nuke to task list