ci: ios swift xcodegen cleanup

[armcknight]

now that the original tracked iOS-Swift.xcodeproj is gone, we don't need to disambiguate the other projects with a _xcodeproj suffix (really was only necessary for the new xcodegen-managed iOS-Swift xcode project but i used it for all of them anyways) and move the iOS-Swift sources one level up from //Samples/iOS-Swift/iOS-Swift to //Samples/iOS-Swift.

Follows the xcodegen work after #5117

#skip-changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.775%. Comparing base (297e221) to head (561314c).

Additional details and impacted files

@@                         Coverage Diff                          @@
##           armcknight/ci/ios13-swift-xcodegen     #5118   +/-   ##
====================================================================
  Coverage                              92.775%   92.775%           
====================================================================
  Files                                     677       677           
  Lines                                   84281     84271   -10     
  Branches                                30669     30654   -15     
====================================================================
- Hits                                    78192     78183    -9     
+ Misses                                   5987      5984    -3     
- Partials                                  102       104    +2     

see 8 files with indirect coverage changes

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Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1223.88 ms	1239.85 ms	15.98 ms
Size	22.31 KiB	851.56 KiB	829.26 KiB