BRUSSELS — A €20 billion pact to carve up French telecoms company SFR is shaping up to become a major test of the EU’s readiness to abandon decades of caution and allow merger megadeals. Operators Bouygues, Orange and Iliad agreed Saturday night on a three-way undertaking to acquire SFR from Patrick Drahi. The deal, the companies announced, would “strengthen the sector’s long-term capacity to invest, innovate, and anticipate major technological developments.” The tie-up faces a lengthy path to