Risk Calculation Errors - Alert Refinement

[SebastianWild]

Checklist

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Description

Previously, UIAlertControllers triggered by the app because of a failed exposure detection (when an ExposureDetection.DidEndPrematurelyReason is thrown) would have a simple OK button and nothing else. This PR adds some more details, as well as links several ENErrors to their corresponding FAQ entries:

• ENError(.unsupported) -> FAQ
• ENError(.internal) -> FAQ
• ENError(.rateLimited) -> FAQ

Alert before:

Alert after:

[SebastianWild]

I shifted these around as they are used in several places (not just ExposureSubmission) anymore.

[melloskitten]

Rewrote the Exposure Submission error handlings to use these links, removed the old traces of the links.

[SebastianWild]

This extension seems like it could go into a separate file, but I wasn't sure if it's worth it as it's only used here.

It is not private as we'd like to unit test it.

[melloskitten]

Moved this to a separate extension, and added the ExposureSubmission stuff into it as well. Check Error+FAQUrl.swift for this change.

[SebastianWild]

I left these be in order to not change too many unrelated files in this PR, but we can certainly adjust the references where they're used.

[melloskitten]

I am going to adjust these in the Exposure Submission flow to get rid of the indirection.

[haosap]

Hi @kaluju ,
Could you please review the resources files?
Thanks.

[kaluju]

The new error message looks fine.

[melloskitten]

PLEASE DO NOT MERGE THIS. I want to do adjustments.

[melloskitten]

I have merged the exposure submissions errors & the errors introduced in this pull request to the best of my knowledge, in order to remove duplication and have a more pleasant code base. Thanks to @johannesrohwer for helping me check for consistencies. Please check the changes again, if you'd be so kind.