Migrate to targeted Swift Concurrency checking

[samsymons]

Task/Issue URL: https://app.asana.com/0/1199230911884351/1203759366656777/f
Tech Design URL:
CC: @mallexxx

Description:

This PR sets the macOS browser to use Targeted Swift Concurrency checks, and resolves warnings that came up when making that change.

Steps to test this PR:

1. Build the app and check that no concurrency warnings appear (including for the test suite)
2. Check that the Fire button works as expected
3. Check that Lottie animations work as expected
4. To be really cautious, check that the NSException extension works as expected. Something like this should do it:

        do {
            try NSException.catch {
                let name = NSExceptionName(rawValue: "Name")
                let exception = NSException(name: name, reason: "Reason", userInfo: ["key": "value"])
                exception.raise()
            }
        } catch {
            print(error)
        }

Testing checklist:

• Test with Release configuration
• Test proper deallocation of tabs
• Make sure committed submodule changes are desired
• Make sure configuration is changed only in xcconfig files, not in the Xcode project file directly

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Internal references:

Software Engineering Expectations
Technical Design Template
When ready for review, remember to post the PR in MM

[samsymons]

These still conform to the error protocols that require them, so this shouldn't affect the behaviour of the app when receiving an exception. This change was made as NSException doesn't conform to Sendable but Swift.Error does, so I've extracted out only the values of the exception that we use.

[samsymons]

This should go away once we upgrade our Lottie version, but the latest version of Lottie doesn't work perfectly with our animations. I plan to request permission to pull our animation files out into a sample app and send it to the Lottie maintainers during my next maintenance days, as we're blocked from upgrading until they work again.

[samsymons]

This doesn't really change any behaviour since this protocol wraps a type that needs to be on the main thread anyway, but the compiler isn't yet smart enough to know that so this just makes it happy.

[tomasstrba]

LGTM! 👍 This is great! 🥇