Trent Williams, at age 37 and entering his 16th year in the NFL, lined up at left tackle and took on all comers Thursday in his first full-team action at 49ers training camp. A familiar foe also came forth in Nick Bosa, much to the delight of the 49ers’ three-time All-Pro blindside protector. “Being able to size yourself up against him, especially me going into 16 and not knowing where that cliff is, I get to go against Nick to give me a good measuring stick,” Trent Williams said.