By Huw Jones LONDON (Reuters) – Compressing Britain’s two company listing segments to attract more tech firms could put an existing “gamechanger” at risk, a top London Stock Exchange official said on Thursday. Britain wants to use its post-Brexit flexibility in financial rulemaking to compete better with New York in company listings, and is trying to persuade chip designer Arm to list in London rather than on Wall Street. The Financial Conduct Authority (FCA) has already eased some listing rules and has proposed going further by merging the standard and more demanding premium listing categorie…