APIv4 - Better handling of output value using GROUP_CONCAT

[colemanw]

Overview

Followup to #20655 to improve output formatting of the GROUP_CONCAT sql function in APIv4

Before

Output formatting disabled if function nested within function

After

Output formatting controlled by the inner function

[civibot]

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[colemanw]

Ping @seamuslee001 can you test this with php8?

[seamuslee001]

I ran the apiv4 unit tests on php8 with this patched and it works merging