Action plugin authors can specify alternative icon path for dark theme.
If it's not specified then standard icon will be used for both light and
dark themes. If neither icon is specified then the default puzzle piece
icon is used.
Fixes#7984
First issue: the C++ action plugins list should be cleared so that any
plugins that fail to reload do not hang around on the toolbar.
This is fixed on the C++ side.
Second issue: inner dependencies of plugins that are modules were not
reloaded before, which broke reloading for many plugin examples out there.
This is fixed on the Python side by keeping track of dependencies and
clearing them out before reloading a module (unfortunately there doesn't
seem to be a way to do this in the standard library)
Fixes https://gitlab.com/kicad/code/kicad/-/issues/7245
pcbnew_action_plug tracks items that were modified within a plugin. In the case of
deletion, the old object is no longer valid. This commit turns off the call to delete
if a plugin is active.