By Dawn Chmielewski and Lisa Richwine LOS ANGELES (Reuters) -Walt Disney Co Chief Executive Bob Chapek announced a major leadership shift on Thursday, promoting Dana Walden to chairman of general entertainment content as the company works to build its streaming television efforts. Walden replaces veteran Hollywood executive Peter Rice, who is leaving Disney. Both executives joined Disney in 2019 when the company acquired entertainment assets from 21st Century Fox. Sources who spoke with Reuters said Rice, who is well-regarded throughout Hollywood, clashed with Disney’s senior leadership. His d…