What is the difference between ShouldProcess and ConfirmAction?

### Description

I've been reading the [documentation regarding ShouldProcess and ConfirmAction](https://github.com/Azure/azure-powershell/blob/main/documentation/development-docs/design-guidelines/should-process-confirm-impact.md).
It is not clear to me what is the difference between the two and/or is there some strong guidance/preference for one or the other.

### Script or Debug output

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### Environment data

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### Module versions

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### Error output

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Start with documentation/development-docs/design-guidelines/should-process-confirm-impact.md and compare its explanations of ShouldProcess and ConfirmAction. Clarify the distinction and any guidance or preference in that document; done means the documentation directly answers the question.

Written by the indexing model from the issue text.