President Joe Biden holds a campaign rally ahead of the state’s Democratic presidential primary in Las Vegas on February 4. Kevin Lamarque/Reuters/FilePresident Joe Biden on Thursday plans to offer a swipe at his presumptive general election opponent while also making implicit acknowledgement of his own age during his State of the Union address, offering a glimpse of how he’ll address the thorny topic that has become a backdrop to his campaign. “My lifetime has taught me to embrace freedom and democracy. A future based on the core values that have defined America: honesty, decency,…