Mini and Chibi Runami Yachiyo

BUR #57405 has been approved by @nonamethanks.

rename mini_yachiyo -> runami_yachiyo_(mini)
rename chibi_yachiyo -> runami_yachiyo_(chibi)

I'm not sure about the naming of these tags but they at least should be disambiguated since Runami Yachiyo is far from being the only Yachiyo on the site.

Re: the naming

I'm not sure whether official materials have anything to say on this, but I would expect the naming to be swapped. The mini version is basically so small that I'd call it chibi, and what's now called chibi I would just call mini.

I support qualifiers but unless "Chibi Yachiyo" has official naming support it seems that it could lead to mistagging.

The bulk update request #57405 (forum #431490) has been approved by @nonamethanks.