Update provider API docs

[yaahc]

Adds guidance on a specific provider API implementation anti pattern that implementers of the error trait should avoid.

resolves #99301 (comment)

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[yaahc]

I put this at the bottom of the existing doc comment but I wasn't sure if I should feature this more prominently, the only issue is I felt like it might be confusing to provide an example of what not to do before an example of how to use it properly, but the pre-existing example is quite long so I also worry that readers will entirely miss the new section.

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[juntyr]

In the final paragraph, there is "otherwords" -> "other words", and "Error" which should link to the Error trait

(unfortunately I couldn't review in-line since my app bugged out)