Mass update touhou-only tags to avoid mistagging

BUR #2834 has been approved by @NWF_Renim.

mass update gap -> gap_(touhou)

Since it's used exclusively for Touhou, i feel like this distinction helps making the tag less prone to mistagging.

EDIT: The bulk update request #2834 (forum #167793) has been approved by @NWF_Renim.

While i'm at it, there are various touhou-only tags that need some discourse.

Control rod could be in theory nuked (heh) instead of just being updated, but some people use other arm-cannon designs for Okuu, and it could also appear on posts where it isn't actually worn, like post #3918956.

I don't have any other tag in mind currently, but i will post them here if i run into them.

The bulk update request #2834 (forum #167793) has been approved by @NWF_Renim.