fix: allow DatabaseMetaData.getColumns to describe an unset scale

[crwr45]

fix: allow DatabaseMetaData.getColumns to describe an unset scale

getColumns returns a 0 for the scale of a Decimal or Numeric column when the
scale is 0, and when the scale is null. The caller can then not differentiate
between a 0 or a null without another query.

This change replaces the 0 in the ResultSet for scale with a null when describing
an unscaled Decimal or Numeric column. getInt will still convert the null to a 0,
but the caller can then use wasNull() to find out if the underlying value was 0
or null.

This addresses #1712. It is a breaking change, but if the correct getter
(getInt) is used for the column, there is no difference. Other getters may behave
differently.

Signed-off-by: crwr45 charlie.wheelerrobinson@gmail.com

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[codecov-io]

Codecov Report

Merging #1716 into master will increase coverage by 2.67%.
The diff coverage is 33.33%.

@@             Coverage Diff              @@
##             master    #1716      +/-   ##
============================================
+ Coverage     68.26%   70.93%   +2.67%     
- Complexity     4145     4693     +548     
============================================
  Files           187      189       +2     
  Lines         17193    19550    +2357     
  Branches       2852     3482     +630     
============================================
+ Hits          11736    13868    +2132     
- Misses         4180     4274      +94     
- Partials       1277     1408     +131