These are statically discovered using #17670.
This migrates all usages of omitempty to instead use omitzero
where it is safe to do so. These should behave the same as before,
but allow the behavior to be identical between v1 and v2.
Updates tailscale/corp#791
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
fad54d7c20