PG: implement differed creation of tables to capture all attribute and geometry column creations into a single CREATE TABLE statement. Previous behaviour can be still used with defining the OGR_PG_DIFFERED_CREATION configuration option to NO (#5547)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27476 f0d54148-0727-0410-94bb-9a71ac55c965