af: Add unit test files to macOS workspace [SDK-4702] 2/2

[Widcket]

• [ ] All new/changed/fixed functionality is covered by tests (or N/A)
• [ ] I have added documentation for all new/changed functionality (or N/A)

📋 Changes

This PR adds all the existing Swift unit test files to the macOS workspace, so they can run on macOS.

Also, the default RunnerTests.swift file was deleted for both macOS and iOS.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (9cfa40d) 96.36% compared to head (9382877) 96.36%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## macos-support/example-app-macos #355 +/- ## ================================================================ Coverage 96.36% 96.36% ================================================================ Files 98 98 Lines 1596 1596 Branches 328 328 ================================================================ Hits 1538 1538 Misses 50 50 Partials 8 8 ``` | [Flag](https://app.codecov.io/gh/auth0/auth0-flutter/pull/355/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | Coverage Δ | | |---|---|---| | [auth0_flutter](https://app.codecov.io/gh/auth0/auth0-flutter/pull/355/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | `100.00% <ø> (ø)` | | | [auth0_flutter_android](https://app.codecov.io/gh/auth0/auth0-flutter/pull/355/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | `97.35% <ø> (ø)` | | | [auth0_flutter_ios](https://app.codecov.io/gh/auth0/auth0-flutter/pull/355/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | `99.85% <ø> (ø)` | | | [auth0_flutter_platform_interface](https://app.codecov.io/gh/auth0/auth0-flutter/pull/355/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | `87.03% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#carryforward-flags-in-the-pull-request-comment) to find out more.

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