IFNG and cerebral infarction: Inhibited neuronal apoptosis, relieved cerebral infarction, degraded the release of IL‐6, TNF‐α, IFN‐γ and IL‐17, decreased Verrucomicrobia, Akkermansia and Tenericutes, increased Tenericutes and Prevotella_copri, and ameliorated the permeability of BBB