Fix the following Docker image build warning that stops privnet image build:
```
1 warning found (use docker --debug to expand):
- FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 3)
```
Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>
Don't need to keep the copy of the official Golang image in our
dockerfile, let's use it as a base builder image.
Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>
Turns out that caching the golang:windowsservercore-ltsc2022 image between
GithubAction workflow runs is a bad idea because `docker load` command still takes
too long to load image from cached archive (~9-10min on standard windows runner).
And after that runner still needs to build the neo-go image itself.
However, standard GA windows runner is supplied with prefetched latest
mcr.microsoft.com/windows/servercore:ltsc2022 image, so using it costs almost
nothing. Thus, the other approach is implemented: we use standard
mcr.microsoft.com/windows/servercore:ltsc2022 image as both build-base and
final-base. Then we install all required tools for building neo-go manually
on build-base image (these tools are git and go 1.17). Compared to the first
approach, the publishing job (included build and publish to DockerHub)
takes ~7-8min to finish.
