Error FileLoader not found

Problem/Motivation

When enabling the module, an exception is thrown that the "FileLoader" is not found.
This is due to the use of the AutoconfigureTag Attribute which imposes an implicit dependency on symfony/config which is not a dependency of drupal core.

Proposed resolution

Move service tags to the service.yml file.
WARNING: this also introduces a breaking change, due to the yaml service definition not supporting non-scalar values for tag parameters.