Optimize DecimalColumnSetter for each database implementations

Some database (or JDBC) implementations can convert integer or double into decimal column.
In this case, Java code doesn't have to instantiate BigDecimal object.

Start by locating DecimalColumnSetter and tracing how integer and double values are handled for the database or JDBC implementations. Identify which implementations can accept those values directly, then verify that decimal output remains correct without unnecessary BigDecimal construction. The issue is done when the supported implementations are optimized and their existing tests still pass.

Written by the indexing model from the issue text.