feat: improve DX of csv_agg with csv_options

[steve-chavez]

Now we use the following interface for the agg:

SELECT csv_agg(x, csv_options(';'))
SELECT csv_agg(x, csv_options(delimiter := '|'))

SELECT csv_agg(x) -- works as usual

This using a composite type plus a function constructor.

Also bumps version to 0.2.

[coveralls]

Pull Request Test Coverage Report for Build 16811811075

Details

• 27 of 27 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.5%) to 96.739%

---

Totals
Change from base Build 16811033597:	0.5%
Covered Lines:	89
Relevant Lines:	92

---

💛 - Coveralls