Don't format options table like errors

[Thomas1664]

The output of vcpkg help <command> was formatted like an error message.

To fix this, I renamed print_usage to usage_for_command and made it return a LocalizedString instead of printing as an error message right away. This allows a more flexible use of this function.

I also changed consumers to print this to stdout in order to be consistent with surrounding messages

[BillyONeal]

Printing this to stderr seems correct, since it is printed when there has been a failure. The resolution of #1175 was that we wanted to avoid using more than one stream in most cases to avoid synchronization problems in tools that log the streams separately.

[Thomas1664]

Printing this to stderr seems correct, since it is printed when there has been a failure.

This doesn't change with this PR. However, the options table is also used for the help command in which case the rest of the output goes to stdout. This is what this PR fixes.

[BillyONeal]

This LGTM with a few end to end tests added:

• vcpkg help output going to stdout
• vcpkg help not-a-topic output going to stderr
• vcpkg not-a-command output going to stderr
• vcpkg install --not-a-switch output going to stderr

[BillyONeal]

This doesn't change with this PR. However, the options table is also used for the help command in which case the rest of the output goes to stdout. This is what this PR fixes.

Good point!

[Thomas1664]

• vcpkg help output going to stdout
• vcpkg help not-a-topic output going to stderr
• vcpkg not-a-command output going to stderr
• vcpkg install --not-a-switch output going to stderr

I want to emphasise that in all 3 error cases all of the output went to stdout. I changed this to stderr in 21e9c58.

This LGTM with a few end to end tests added:

I don't have any experiences with PowerShell or how the end to end tests work.

[BillyONeal]

I don't have any experiences with PowerShell or how the end to end tests work.

I added them

[BillyONeal]

Thanks :)