Adapt Puma config to support Puma 7

What does this MR do?

The Puma configuration template needs to be adjusted to work with Puma 7:

1. The callback hooks have been renamed in https://github.com/puma/puma/pull/3438:

   • on_worker_boot -> before_worker_boot
   • on_worker_shutdown -> before_worker_shutdown
   • on_restart -> before_restart

This commit adds a conditional block based on the Puma version to use the new hooks.

2. With https://github.com/puma/puma/pull/3297, Puma 7 raises an exception if Puma's options are accessed before they are fully loaded. Currently we pass these options during loading of the Puma config file, which then triggers this exception. These options are used to determine whether Puma is in clustered mode by checking the number of workers.

This commit uses a new method set_puma_worker_count added in gitlab!204104 (merged).

Note that Puma 7.0.2 or higher is required because https://github.com/puma/puma/pull/3731 fixes an upstream bug to make Puma 7 work with queue_requests set to false.

set_puma_worker_count was added in gitlab!204104 (merged).

The GDK config was also adapted similarly in gitlab-development-kit!5249 (merged).

Related issues

Checklist

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Required

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• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.