Add swivel guns and make cannon shots more like special attacks

TL;DR: Add swivel guns as our regular attacks, make cannons our special attacks with special effects.

Swivel guns are small cannons mounted on a swivelling stand that would better fit how we use cannons currently in Sailing, both from a functional and visual perspective. They would also provide a potential solution to the ammo issue.

Firing our cannons looks weird with our cannon shots flying out of the barrel sideways, feels weak with any enemy taking numerous rounds to kill, and is expensive thanks to that high ammo usage. A swivel gun would be able to swivel towards the enemy and look better, feel less weak for their size, and would use smaller ammunition allowing far greater amounts to be granted and believably.

Cannons would then be free to take on another, more impactful role. I suggest treating them more like special attacks wherein they can be used relatively infrequently but have far greater effects when they do hit. This could include simply doing massive damage, stunning enemies, breaking enemy armour (reducing an enemy's flat armour perhaps?), or by being able to signficantly damage other ships and structures (if they wanted to add ship vs ship combat and sieges for example)

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Some further suggestions for these forms of cannons is to implement timed attacks and/or aimed attacks:

• Timed attacks: some enemies aren't always vulnerable to cannon shots, simply because they're underwater in most cases. They instead occaissionally perform a telegraphed move which leaves them vulnerable. You need to fire your cannons in this window to land the shot.
• Aimed attacks: Cannons can't swivel, so you have to aim them by moving your boat. Larger boats with longer cannon batteries have a more generous area where enemies are considered "in sight" and can be hit.

The idea behind these is to make using the cannons more interesting and require more skill than just clicking a special attack bar, and to provide another excuse to crank up each individual shot's impact.