By Kate Holton and Elizabeth Piper LONDON (Reuters) -Britain on Wednesday rejected European Union proposals to resolve a standoff over post-Brexit trade rules for Northern Ireland, saying it would not shy away from taking direct action in the latest escalation between the two sides. Striking a deal that preserved peace in Northern Ireland and protected the EU’s single market without imposing a hard land border between the British province and EU member state Ireland, or a border within the United Kingdom, was always the biggest challenge for London as it embarked on its exit from the bloc. It …