lc0 --help doesn't work; uses stderr instead of stdout

[Technologov]

Standard Linux command like this fails:
./lc0 --help | more

Namely: all help is displayed as one huge mega-page, completely unreadble by humans. The pipe more doesn't work, because it uses stdout, which is empty buffer.

But redirecting stderr to STDOUT works:
./lc0 --help 2>&1 |more

Please redirect all output to STDOUT, where it should belong.

[mooskagh]

There are different opinions on the internet, but majority indeed seems to be inclined towards help going to stdout.

Feel free to send a PR if you have time. All is needed is replace all cerr with cout in
OptionsParser::ShowHelp():
https://github.com/LeelaChessZero/lc0/blob/407be4d0bd480cb1a56e8bd86dcc3d5d8d58c6e7/src/utils/optionsparser.cc#L241