Rename "water battle" -> naval battle

BUR #16478 has been approved by @nonamethanks.

rename water_battle -> naval_battle

I don't know who comes up with the tag name "water battle", but I'm pretty sure nobody used that term to refer to any combat on and below the water surface. So I think it should be renamed into the actual word used to describe this specific combat aka "naval battle" instead.

Looking at the early posts tagged with it, looks like the tag was added by a single user back in 2010 that I feel was close to be a (later abandoned) pet tag and was originally for any battle (but not warship battle, oddly enough) that happened on or in the water.

The bulk update request #16478 (forum #239791) has been approved by @nonamethanks.