Better handling of ambiguous errors in snforge plugin

[cptartur]

Currently, for all attributes in snforge plugin where multiple valid options are valid (e.g. fork), in case of any error, we always display All options failed: ... Resolve at lest one of them.

Change the plugin logic, so, where possible, we only display the relevant failed option(s). Only show the "All options failed ..." when the provided input is truly ambiguous.

E.g. if user provides an invalid URL, do not show an error regarding invalid fork name.