[Balance Idea]: Remove ACU blocking with unbuild PDs/Walls

[Basilisk3]

Intended Change

Currently it is possible to permanently block ACUs with unbuilt buildings, such as Tech 1 PDs. This should not be possible for several reasons:

• It can cause ACUs to be stuck inside the PD, making it almost impossible to escape
• It shifts the balance of the game towards making ACU pushes or small micro mistakes very punishing. This stands in contrast with a wide range of balance changes that have been made in the past to allow for more liberal usage of the ACU. See the changes to unit density etc.
• It abuses pathfinding problems to create an advantage
• It is very unintuitive and disruptive

Possible workarounds:

• Fixing it via code, for example by speeding up the rate at which PDs decay. Unfortunately this is likely handled by the engine. Introducing a limit on how quickly Tech 1 PD selection can be spammed might be reasonable to do in LUA.
• Making it an exploit

Reasoning

Here is an example of this happening (thank you to @lL1l1 for posting it on Discord):

https://cdn.discordapp.com/attachments/476200727912644618/1329258619711131740/wall_block_bm.mp4?ex=6789b00f&is=67885e8f&hm=aff848fbcfa4caf18ca68a4707eb18290cfd0b3172a96f1893c8af32563b8188&

Please note that with more training (and some other tricks I won't mention here) it can be even more effective than shown in the video.

Expected behavior

Blocking ACUs with buildings is fine, blocking them permanently is a no-go.