By Rowena Edwards and Bozorgmehr Sharafedin LONDON (Reuters) – The European Union has proposed a phased embargo of Russian oil but may find it tricky to implement, given Europe’s complex distribution network and challenges in tracking crude once it is blended or refined. The plan, if agreed by member states, would take effect in six months for crude, and in eight months for diesel and other oil products. HOW WATERTIGHT WILL ANY EU SANCTIONS BE? Under the proposal, Hungary and Slovakia would be granted a longer period – until the end of 2023 – to adapt to the embargo. This means that countries …