[TTI] Add OperandValueProperties::OP_NegatedPowerOf2 enum (PR51436)

The mul by constant costmodels handle power-of-2 constants, but not negated-power-of-2, despite the backends handling both.

This patch adds the OperandValueProperties::OP_NegatedPowerOf2 enum and wires it for use for basic mul cost analysis and SLP handling.

Fixes #50778

Differential Revision: https://reviews.llvm.org/D111968