feat: allow controlling when a fixture is rendered

[alestiago]

Description

Changes _renderFixtures to renderFixture. This keeps the consistency with the other public render methods in BodyComponent.

Introduces new functionalities:

• Allow listening when a given fixture is rendered
• Allows modifying the rendering logic for a given (one or more) fixtures.

For example, avoiding a fixture to be rendered:

class MyBodyComponent extends BodyComponent {
...
void renderFixture(Canvas canvas, Fixture fixture) {
 final avoidRendering = condition; // Any condition here.
  if (avoidRendering) return;
  super.renderFixture(canvas, fixture);
}
...
}

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

Related Issues

[spydon]

I don't think we should rely on userdata for this (preferably we shouldn't rely on userdata for anything, it is a way too fragile pattern).

[alestiago]

(cc: @spydon )

This PR is an initial proposal to filter the rendering of some fixtures. Once settled, I'll update tests, examples and docs.

[alestiago]

I don't think we should rely on userdata for this (preferably we shouldn't rely on userdata for anything, it is a way too fragile pattern).

Thanks @spydon for having a look. One doesn't need to rely on userData, as pointed out in the description, one can store those fixtures that would be skipped during rendering and check against that list.

Is up to the developer how they wish to filter the fixtures. For example, if they don't want to render edge sapes, they can check for it.

I've updated the example, since using userData is discouraged.

[alestiago]

Sorry for the delay on this open PR. Been busy, I will like to prioritise it this weekend.

[spydon]

Great with some goldens here too :)
You don't have to put flame_forge2d in the scope that is already derived from what files that are changes, the scope is more if you have a bigger epic that you're working on for example.

[luanpotter]

LGTM with one comment. Nice tests!