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 https://github.com/flame-engine/flame/pull/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

• [x] I have followed the Contributor Guide when preparing my PR.
• [x] I have updated/added tests for ALL new/updated/fixed functionality.
• [x] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [x] I have updated/added relevant examples in examples or docs.

Breaking Change?

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