[2/3] Timer refactor: TIMG

[MabezDev]

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Submission Checklist 📝

• [x] I have updated existing examples or added new ones (if applicable).
• [x] I have used cargo xtask fmt-packages command to ensure that all changed code is formatted correctly.
• [x] My changes were added to the CHANGELOG.md in the proper section.
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Pull Request Details 📖

Description

Part 2 which simplifies the TIMG timers. All sub timers now have the same type erased type: Timer. I also managed to dedupe and remove the instance trait completely (the instance trait for TIMG still exists), which is a huge code saving.

[MabezDev]

Skip changelog for the same reasons as part 1