Adopt Swift Testing

[SimplyDanny]

Swift Testing requires all builds to run on Swift 6.1.

[SwiftLintBot]

	2 Warnings
⚠️	Big PR
⚠️	If this is a user-facing change, please include a CHANGELOG entry to credit yourself! You can find it at CHANGELOG.md.

	18 Messages
📖	Building this branch resulted in a binary size of 26172.54 KiB vs 26172.8 KiB when built on main (-1% smaller).
📖	Linting Aerial with this PR took 0.8 s vs 0.83 s on main (3% faster).
📖	Linting Alamofire with this PR took 0.98 s vs 1.01 s on main (2% faster).
📖	Linting Brave with this PR took 6.81 s vs 6.83 s on main (0% faster).
📖	Linting DuckDuckGo with this PR took 20.85 s vs 20.84 s on main (0% slower).
📖	Linting Firefox with this PR took 10.77 s vs 10.77 s on main (0% slower).
📖	Linting Kickstarter with this PR took 7.6 s vs 7.61 s on main (0% faster).
📖	Linting Moya with this PR took 0.45 s vs 0.43 s on main (4% slower).
📖	Linting NetNewsWire with this PR took 2.37 s vs 2.35 s on main (0% slower).
📖	Linting Nimble with this PR took 0.67 s vs 0.63 s on main (6% slower).
📖	Linting PocketCasts with this PR took 6.66 s vs 6.67 s on main (0% faster).
📖	Linting Quick with this PR took 0.43 s vs 0.39 s on main (10% slower).
📖	Linting Realm with this PR took 3.33 s vs 3.3 s on main (0% slower).
📖	Linting Sourcery with this PR took 1.8 s vs 1.8 s on main (0% slower).
📖	Linting Swift with this PR took 4.12 s vs 4.09 s on main (0% slower).
📖	Linting VLC with this PR took 1.12 s vs 1.13 s on main (0% faster).
📖	Linting Wire with this PR took 17.17 s vs 17.15 s on main (0% slower).
📖	Linting WordPress with this PR took 11.24 s vs 11.21 s on main (0% slower).

Here's an example of your CHANGELOG entry:

* Adopt Swift Testing.  
  [SimplyDanny](https://github.com/SimplyDanny)
  [#issue_number](https://github.com/realm/SwiftLint/issues/issue_number)

note: There are two invisible spaces after the entry's text.

Generated by 🚫 Danger