fix: Fix monster faction debugmsg after monster::poly

[Coolthulhu]

Purpose of change (The Why)

Fix #3072

Describe the solution (The How)

Update monster's faction in monster tracker, if the tracker contains said monster.

Describe alternatives you've considered

Only updating the faction in tracker if it actually changed.

Testing

1. Clean map of monsters
2. Spawn zombie dog
3. Surround dog with goo pits
4. Spawn light turret where it can see the dog and will target it
5. Wait a turn
6. The dog should walk onto a pit, polymorph into a slime, then get shot (it must all happen in the same turn)

Additional context

Checklist

Mandatory

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax like closes #1234 in Summary of the PR so it can be closed automatically.
• I've committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.