exit code does not indicate failure when credentials are not found

[chuckries]

gcm-core.exe appears to always return 0 even if the credentials were not found. This does not match the behavior that legacy gcm did and it makes leveraging it outside of git scenarios more difficult.

D:\VisualStudio\2022\main\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\libexec\git-core>git-credential-manager-core.exe get
protocol=https
host=github.com

fatal: Cannot prompt because user interactivity has been disabled.

D:\VisualStudio\2022\main\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\libexec\git-core>echo %ERRORLEVEL%
0

D:\VisualStudio\2022\main\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\libexec\git-core>git-credential-manager.exe get
protocol=https
host=github.com

Logon failed, use ctrl+c to cancel basic credential prompt.

D:\VisualStudio\2022\main\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\libexec\git-core>echo %ERRORLEVEL%
-1

D:\VisualStudio\2022\main\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Git\mingw32\libexec\git-core>git-credential-manager-core.exe --version
2.0.475+27fbadca1d

[mjcheetham]

Ah yes.. this change would have come about when we moved to using System.CommandLine for command handling.
Got a PR up to return -1 on exception, such as when interaction has been disabled #441