feat: Add basic infrastructure for a Context API [PROPOSAL][WIP]

[luanpotter]

Description

The idea is to provide some sort of "context" API for components to share render-time information with indirect descendants.

Use cases can include:

• the currentCamera value which is currently handled as a global list
• shader rendering information (to replace the custom Canvas implementation from feat: Fragment shaders pipelines and Camera based post processing #3404 - @renancaraujo lmk what you think!

Pending some benchmarking to confirm it does not increase latency but requesting for comments on the proposed API.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• 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 or docs.

Breaking Change?

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

[renancaraujo]

Looking good. API wise it is good enough as an approach that it is not a breaking change.

It seems specific to the render phase, so I would add user-friendly error messages for when users try to access the context outside of render.
Also, should we name it RenderContext since it is so specific?

[luanpotter]

@renancaraujo agree with both!

[spydon]

I'd just like some benchmark of the implication of adding this, other than that I think it looks good!

[github-actions]

Benchmark Results

Package flame:

• Current Branch [luan.context-api]: 2791.834 μs
• Base Branch [main]: 2687.456 μs
• Diff: 🔴 +3.884 %

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Benchmarks provided with 💙 by Dart Benchmark Action.

[luanpotter]

(note: I will add a bench specifically about rendering when I have some time. this was just testing the waters with the action)