Fedora 35 support was dropped, so we can update to a newer Go.
Stable RHEL 8 and 9 and Fedora 36 ships Go 1.18, so let's switch to it.
"//go:build" directives are now apparently enforced by go fmt, so that's why
there were added.
Also, all the github actions were adjusted to use Go 1.18.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
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