Added new method remove to PluginGroup, also adds unit tests for PluginGroup

[blaind]

As requested in #2166

[mockersf]

why not use the disable method?

[blaind]

why not use the disable method?

The root use case here is to reconfigure RenderPlugin with other config (needed, because some initialization is done in build method that depends on the configuration). disable won't work for that (agreed, the remove -approach is not the best either)

pub fn add_plugins_fn(group: &mut PluginGroupBuilder) -> &mut PluginGroupBuilder {
    group.remove::<bevy_render::RenderPlugin>();
    group.add_after::<bevy_scene::ScenePlugin, _>(bevy_render::RenderPlugin {
        base_render_graph_config: Some(bevy_render::render_graph::base::BaseRenderGraphConfig {
            add_2d_camera: false,
            add_3d_camera: false,
            add_xr_camera: true,
            ..Default::default()
        }),
    });

    group
}

[mockersf]

the bug on disabling a plugin and re-adding it with another config is fixed in #2039 👍

[blaind]

That's great! I guess renders this PR as obsolete. Seems to contain tests as well

[alice-i-cecile]

Are we good to close this PR then? :)

[blaind]

Are we good to close this PR then? :)

Ok for me, if there's no other use cases for the remove method

[alice-i-cecile]

I don't see any other immediate application of this functionality so I'm going to close this for now. This can be revived if a use case comes up :)