Rollup merge of #139084 - petrochenkov:transpaque, r=davidtwco

hygiene: Rename semi-transparent to semi-opaque

"Semi-transparent" is just too damn long for a name, especially when used multiple times on a single line, it bothered me when working on #139083.

An optimist sees a macro as semi-opaque, a pessimist sees it as semi-transparent.
Or is it the other way round?

Author: matthiaskrgr