Add a debug mode

[jajm]

It would be useful to be able to turn on a "debug" mode that:

• set the 'debug' parameter on each Solr queries (https://solr.apache.org/guide/8_11/common-query-parameters.html#debug-parameter)
• log all requests and responses

Questions:

• Configurable in config.local.php or in the admin interface ?
• Same log file as Omeka or different log file ?
• Configurable debug value ? (query, timing, results, all)