Type Annotations: core.plugin

[derks]

Add initial type annotations.

Related:

• PR Add python type hints and mypy static type checker #628

Current Errors:

|> cement-py312 <| src # make comply-typing | grep core/plugin
cement/core/plugin.py:8: error: Call to untyped function "minimal_logger" in typed context  [no-untyped-call]
cement/core/plugin.py:26: error: Function is missing a type annotation  [no-untyped-def]
cement/core/plugin.py:37: error: Function is missing a type annotation  [no-untyped-def]
cement/core/plugin.py:48: error: Function is missing a return type annotation  [no-untyped-def]
cement/core/plugin.py:48: note: Use "-> None" if function does not return a value
cement/core/plugin.py:53: error: Function is missing a return type annotation  [no-untyped-def]
cement/core/plugin.py:53: note: Use "-> None" if function does not return a value
cement/core/plugin.py:58: error: Function is missing a return type annotation  [no-untyped-def]
cement/core/plugin.py:58: note: Use "-> None" if function does not return a value
cement/core/plugin.py:63: error: Definition of "Meta" in base class "PluginInterface" is incompatible with definition in base class "Handler"  [misc]
cement/core/plugin.py:63: error: Definition of "Meta" in base class "Interface" is incompatible with definition in base class "Handler"  [misc]
make: *** [Makefile:33: comply-typing] Error 1