SearchKit - Add 'array' option to download API and add test

[colemanw]

Overview

This adds a new option to the SearchKit "Download" api to return a normal array result, which makes testing easier.

Before

Download api would directly output a file to the browser. No working unit test.

After

New option to not directly output file. Unit test works.

[civibot]

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[demeritcowboy]

Looks good.

Minor notes:

• The comment on line 64 is left over from an earlier iteration.
• In terms of docs, I tried running what api explorer suggested: cv ev "$x = \Civi\Api4\SearchDisplay::download(FALSE)->setSavedSearch('abc')->setDisplay('def')->execute(); foreach ($x as $y) { print_r($y); }" but I was only able to get the header row. There is no setLimit(). I didn't bother looking further. The explorer itself does seem to return them all.

[colemanw]

Thanks @demeritcowboy