Remove monolog dependency & use event dispatcher to debug queries

This PR does many things related to query debugging:

 * Remove Monolog dependency
 * Rename `Fridge\DBAL\Logging\Debugger` to `Fridge\DBAL\Debug\QueryDebugger`
 * Remove `QueryDebugger::start` method & move the code in the constructor.
 * Remove `QueryDebugger::toString` & `QueryDebugger::toArray` which only makes sense with Monolog.
 * Add a debug parameter in the `Fridge\DBAL\Configuration` in order to enable/disable the debugging (disable by default)
 * Create a `DebugQueryEvent` which wraps an instance of the `QueryDebugger`.
 * Dispatch the new event (`Events::DEBUG_QUERY`) after a query execution.