go: Update to version 1.20.4

- Update from version 1.15.4 to 1.20.4
- Update of x86_64 rootfile
   aarch64 rootfile needs to be created on a aarch64 build system
- Changelog is very large. For details see https://go.dev/doc/devel/release
   50 mentions of security fixes in the changes from 1.15.4 to 1.20.4

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>