pgsql: Add tests for more row patterns with COPY FROM .. (ON_ERROR igno

Add tests for more row patterns with COPY FROM .. (ON_ERROR ignore)

While digging into the code of this feature, I got confused by the fact
that a line is skipped when a value cannot be converted to its expected
attribute even if the line has fewer attributes than the target
relation. The tests had a check for the case of an empty line, this
commit a couple more patterns where a line is incomplete, but skipped
because of a conversion error.

Reviewed-by: Bharath Rupireddy
Discussion: https://postgr.es/m/Ze_7kZqexdt0BiyC@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a189ed49d6292979be1478292246be61c4563043

Modified Files
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src/test/regress/expected/copy2.out | 5 +++--
src/test/regress/sql/copy2.sql | 3 +++
2 files changed, 6 insertions(+), 2 deletions(-)