fix: preserve target faction in rename events

[BriceFab]

Fixes #57.

FactionRenameEvent currently derives its faction from the command sender, which causes administrative faction renames to expose the administrator's faction instead of the faction actually being renamed.

This change:

• adds a constructor accepting the target Faction explicitly;
• preserves the existing constructor for backwards compatibility;
• passes the target faction when firing rename events;
• adds regression tests for both administrative and regular faction renames.

[mbax]

Fixed in ee89730