2023-July-15 - 2.6.14415

Fix another cause of "Could not find step name" (2.6 bug). (#11780)

This one is caused by non-determinism when choose an arbitrary unit type in a firing group to name that group. When the ordering of the provided units changed during the rounds of a battle, it resulted in different step names generated. This PR fixes that problem by choosing the first name alphabetically.

Adds test coverage.