feat: add header to csv_options

[steve-chavez]

Adds the option to do:

select csv_agg(x, csv_options(header := false)) from projects x;
      csv_agg
-------------------
 1,Windows 7,1    +
 2,Windows 10,1   +
 3,IOS,2          +
 4,OSX,2          +
 5,Orphan,
(1 row)

[coveralls]

Pull Request Test Coverage Report for Build 16818504259

Details

• 14 of 15 (93.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 97.0%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/pg_csv.c	14	15	93.33%

Totals
Change from base Build 16818049236:	0.1%
Covered Lines:	97
Relevant Lines:	100

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💛 - Coveralls