Day 0 exploit regarding unit tags

The difference of IDs between sequentially created units, regardless of which player created them, is 262144 (for probes) plus/minus 2. This can be used to determine how many units your opponent has created since you last created a unit, which can be used to detect ling rushes and among other things.

Proposed fix: have the protocol make a mapping between real unit id and a random tag, then interchange them where appropriate.

See discussion on the discord regarding this.

Start by reviewing the protocol definitions in s2client-proto and the issue's description of sequential unit IDs. Confirm where unit IDs are exposed and how a real-ID-to-random-tag mapping would affect the protocol. Done means the information leak is removed without breaking unit identification for either player.

Written by the indexing model from the issue text.