Support TiDB unary minus pushdown #10746
Description
Enhancement
TiFlash should support pushing down TiDB unary minus scalar functions (UnaryMinusInt, UnaryMinusReal, UnaryMinusDecimal).
At the moment, plans containing these TiDB signatures cannot be executed in TiFlash with TiDB-compatible semantics. We should add the DAG mapping, dedicated execution functions, and coverage for unit, query, and fullstack execution.