pgsql: Improve wrong-tuple-type error reports in contrib/tablefunc.

Improve wrong-tuple-type error reports in contrib/tablefunc.

These messages were fairly confusing, and didn't match the
column names used in the SGML docs.  Try to improve that.
Also use error codes more specific than ERRCODE_SYNTAX_ERROR.

Patch by me, reviewed by Joe Conway

Discussion: https://postgr.es/m/18937.1709676295@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/76904eda25500dd4c6969f3a2a7c0f00146fd763

Modified Files
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contrib/tablefunc/expected/tablefunc.out |  85 ++++++++++++++--
contrib/tablefunc/sql/tablefunc.sql      |  42 ++++++++
contrib/tablefunc/tablefunc.c            | 169 ++++++++++++++-----------------
3 files changed, 195 insertions(+), 101 deletions(-)