feat(Expander): relative Poincaré inequality for shears and translations with a spectator - #1695

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Not declared at the PR head: `E_ij`, `E_ji`, `P_ij`, `ExactDerandomization.Analysis.Square.square_gap`, `changeF`, `slice_frame`, `frame_gap`, `slice_gap`, `square_gap`. Advisory only; see the job summary.