Move AutoParallel activation checkpointing out of the compile backend

[sanketpurandare]

AutoParallel currently applies FSDP AC tags before compile_with_joint_descriptors, but the auto_parallel backend also runs the AC joint pass. The backend pass preserves the earlier FSDP tags and applies new tags, which can cause FSDP recompute to be represented twice in the backward graph. It may be removed by DCE, but this is a fragmented and fragile path. AC should be applied once during AutoParallel placement, before compilation, and the backend should only configure Inductor bucketing/overlap context.