Expose Nextcloud AIO version if present

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Feature request

Which Nextcloud Version are you currently using:
32.0.5 via Nextcloud AIO 12.6.1

Is your feature request related to a problem? Please describe.
As described in nextcloud/all-in-one#7158, I would like to read out the Nextcloud AIO version with an external tool.

Describe the solution you'd like
I hope this could be added into the response from /ocs/v2.php/apps/serverinfo/api/v1/info. The Nextcloud AIO version is available to the Nextcloud container as an environment variable (NC_AIO_VERSION) and in the system config. So it should be possible to check if that value is set and expose it, if it is.

Describe alternatives you've considered
As suggested in the discussion, it would be possible to write a script to retrieve and expose the value manually, but I think having this supported "natively" would be much easier.

Additional context
nextcloud/all-in-one#7436
nextcloud/all-in-one#7437

Start at the /ocs/v2.php/apps/serverinfo/api/v1/info endpoint and inspect how system configuration values are added to its response. Check how NC_AIO_VERSION or the corresponding system-config value is detected. Done means the response exposes the AIO version when it is set and remains valid when it is absent.