By Gertrude Chavez-Dreyfuss and Davide Barbuscia NEW YORK (Reuters) -A surge in U.S. Treasury bill issuance in recent months has reduced liquidity in the financial sector, stoking investor concerns that funding markets could face a September squeeze. That could create ripple effects through markets by reducing demand for assets like stocks and corporate bonds, and pushing some investors to set cash on the side in anticipation of volatility. Some say there is a mild risk of a repeat of 2019 when a liquid ...