[ticket/12775] Replace functions_container with a container_builder class.
* Nicofuma/ticket/12775: (34 commits)
[ticket/12775] Set dbal.conn.driver as synthetic during installation
[ticket/12775] Add the definition of dbal.conn in fixtures/config/services.yml
[ticket/12775] Inject the connection when created in the container
[ticket/12775] Extract the vars later in install/install_update.php
[ticket/12775] Rename config_php_handler to config_php_file container_builder
[ticket/12775] Set defined_vars as a property of config_php_file
[ticket/12775] Fix doc blocks in the container builder
[ticket/12775] Remove useless includes of config.php
[ticket/12775] Move phpbb_convert_30_dbms_to_31 into the config file class
[ticket/12775] Fix comments
[ticket/12775] Update doc blocks
[ticket/12775] Fix container_builder
[ticket/12775] Rename config_php to config_php_file
[ticket/12775] Renamed to \phpbb\di\container_builder
[ticket/12775] Remove the last include of functions_container
[ticket/12775] Fix unit tests
[ticket/12775] Add tests for \phpbb\config_php
[ticket/12775] Add tests for the container factory
[ticket/12775] Use a field instead of a local var in load_config_var()
[ticket/12775] Update container and config in install/
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