Commit 759be3dad9 bumped our Go
requirement to 1.18 which allows us to drop support for old-style
`+build` tags. This change runs `go fix ./...` to remove them, and
updates some remaining code generators that produced `+build` lines.
* Bump CI to Go 1.19
* Update golang/go edwards25519 test
* Apply formatting to printer stubs output (to get correct comment formatting)
* Bump gofumpt version