225 add a plugin registry

[robsdavis]

Description

This PR allows plugins that have been added by the user at runtime to be stored in the Plugins() context. The most important benefit of which is that it makes these user added plugins available to Benchmarks.evaluate(). This is achieved by the addition of two dictionary objects: "PLUGIN_REGISTRY" and "PLUGIN_CATEGORY_REGISTRY" to plugin.py. These dictionaries store all the plugins that get added by the PluginLoader. A new PluginLoader._refresh() function sets the values of these new dictionaries to self._plugins and self._categories. _refresh is called by all the functions that access the _plugins of _categories attributes, meaning that added plugins are always available.

closes #225

Affected Dependencies

None

How has this been tested?

• New tests added:
  • tests/plugins/test_plugin_add.py checks an added plugin is available from synthcity.plugins.Plugins().list()
  • tests/benchmarks/test_benchmarks.py::test_benchmark_added_plugin checks that added plugins are available to Benchmarks.evaluate()

Checklist

• I have followed the Contribution Guidelines and Code of Conduct
• I have commented my code following the van der Schaar Lab Styleguide
• I have labelled this PR with the relevant Type labels
• My changes are covered by tests