“Tell me your story, and I will tell you who you are.” This line is repeated through the 8-episode first-season run of Apple TV+’s fascinating “The Changeling,” spoken via narration by the author of the acclaimed novel on which it’s based, Victor LaValle. This production is clearly the work of storytellers, people who believe in the power of not just the personal journey but the mythology that still serves as a foundation for so much of the world.