Spirv-fuzz: Support adding precision decorations in TransformationWrapVectorSynonym

Currently, TransformationWrapVectorSynonym (#4322) wrap the operands of a scalar operations into two vectors, perform the same scalar operation between two vectors and add synonym facts between the original scalar instruction id and id from the result vector at corresponding position. However, if operands in the original instruction have RelaxedPrecision decorations, the result id of the corresponding vector operation will not have that.

It would be nice to support adding decoration to the result of added vector operation depending on the type of decorations the original instruction has.

Start by reading the implementation and tests for TransformationWrapVectorSynonym, introduced in issue #4322. Trace how scalar operands are wrapped into vectors and how synonym facts are added. Done means the generated vector result receives the appropriate precision decoration when the original instruction has RelaxedPrecision.

Written by the indexing model from the issue text.