[TypeSize] Extend UnivariateLinearPolyBase with getWithIncrement/Decrement methods
This patch adds getWithIncrement/getWithDecrement methods to
ElementCount and TypeSize to allow:
TypeSize::getFixed(8).getWithIncrement(8) <=> TypeSize::getFixed(16)
TypeSize::getFixed(16).getWithDecrement(8) <=> TypeSize::getFixed(8)
TypeSize::getScalable(8).getWithIncrement(8) <=> TypeSize::getScalable(16)
TypeSize::getScalable(16).getWithDecrement(8) <=> TypeSize::getScalable(8)
This patch implements parts of the POC in D90342.
Reviewed By: ctetreau, dmgreen
Differential Revision: https://reviews.llvm.org/D90713