The last remaining lawsuit over the lethal 2010 San Bruno pipeline explosion moved close to resolution Friday when a judge gave preliminary approval to a $90 million settlement of claims by Pacific Gas and Electric Co. shareholders against the utility’s managers and directors. Under the settlement, the managers and directors, and their insurers, would pay the funds to PG&E, which would use it for programs intended to upgrade gas operations and corporate governance, said Mark Molumphy, a lawyer for the shareholders. The settlement would bring an end to legal proceedings over the September 2010 explosion and fire that killed eight people and destroyed 38 homes. PG&E was also convicted in a criminal trial of five felony violations of pipeline-safety laws, and a sixth charge of obstructing the federal investigation of the explosion.