If the column statistics in `pg_statistic` has values with type
different than column type, metadata accessor should not translate the
stats and create a dummy stats instead.

This commit also reorders stats collection from the `pg_statistic` to
align with how analyze generates stats. MCV and Histogram translation is
moved to the end after NDV, nullfraction and column width extraction.
Signed-off-by: NMelanie Plageman <mplageman@pivotal.io>