Reduce macro usage in PDMA

[Dominaezzz]

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• I have updated existing examples or added new ones (if applicable).
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Pull Request Details 📖

Description

Pull out as much code as possible from the PDMA macros.
My IDE has a better time with code outside macros. If no one else's IDE is bothered by this I'll close the PR.

I've actually gotten the code to the point where I can probably merge the ImplI2sChannel and ImplSpiChannel macros into one macro with a few more parameters.

No changelog since this is an internal refactor.

Testing

It builds, it's just a refactor.

[bugadani]

Not sure why you closed this, I'm pretty sure the change is worth it, unless you have a better idea.

[Dominaezzz]

I remembered what you said in #2196 (comment) and decided to close it, and replace it with #2249 .