Tacmap: aSL's do not change a players' tacmap icon

### Testmerges

#3088, #3185, #3298, #3424, #3430, #3271, #3392

### Description of the bug

When using the tactical map on the CIC overwatch consoles, the icons of marines will not update to reflect their current squad status as acting Squad Leaders.

For example, if you set a rifleman as the acting squad leader, the map will continue to display him as a rifleman, and the actual squad leader will continue to appear as the SL on the tacmap - which can get very confusing.

### What's the difference with what should have happened?

When switching aSL to someone else in a squad, their tacmap icon should change to reflect their current status as SL, and the previous SL's tacmap icon should revert to indicate either that they are no longer SL or that they are their original job icon.

### How do we reproduce this bug?

1. Have an SL for one of the squads planetside
2. Go to an overwatch console for that squad and open the tactical map
3. Observe that the SL appears on the tactical map
4. Set a second marine as the acting squad leader
5. Observe that the SL icon did not swap to the now acting SL and they retain their original job icon still

### Issue Bingo

- [X] Issue could be reproduced at least once
- [X] Issue happened in a recent (less than 7 days ago) round
- [X] Couldn't find an existing issue about this (https://github.com/cmss13-devs/cmss13/issues)

Reproduce the issue from an overwatch console by opening the tactical map, assigning a second marine as acting squad leader, and observing both icons. Trace the tactical-map handling for squad-leader status and verify that the acting leader receives the SL icon while the previous leader reverts to the appropriate non-SL icon.

Written by the indexing model from the issue text.