Eight candidates running to become governor of California have lobbed heated criticism at each other in a chaotic televised debate. The evening was filled with interruptions, tense exchanges and verbal detours — even at times from moderators. Candidates sparred over questions ranging from how to cut gas prices to potential state charges against federal immigration agents to how best to contend with wildfires. The unruly format underscored the instability in a crowded race that has no clear leader, with mail ballots going to voters in less than a week. It is the first time in a generation that California has a wide-open contest for the heavily Democratic state’s highest office.