Add Sendable conformances

[ffried]

These changes are now available in 4.1.0

This adds Sendable conformances to all types in this library.

[ffried]

This currently depends on https://github.com/swift-server-community/APNSwift/pull/195 to be free of warnings, but in general all types should be safe to use across threads.

[ffried]

@0xTim Good point. I had to make the class final however (otherwise, @unchecked would still be necessary). It shouldn't break anything, though, since it was never open - so no subclasses can exist outside of the module.

Also, I removed the unused lock from Application.APNS.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 84.00000% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 89.39%. Comparing base (c1f1030) to head (fc65dcc). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #57 +/- ## ========================================== + Coverage 89.04% 89.39% +0.35% ========================================== Files 4 4 Lines 73 66 -7 ========================================== - Hits 65 59 -6 + Misses 8 7 -1 ``` | [Files](https://app.codecov.io/gh/vapor/apns/pull/57?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor) | Coverage Δ | | |---|---|---| | [Sources/VaporAPNS/Application+APNS.swift](https://app.codecov.io/gh/vapor/apns/pull/57?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9WYXBvckFQTlMvQXBwbGljYXRpb24rQVBOUy5zd2lmdA==) | `91.30% <ø> (-0.37%)` | :arrow_down: | | [Sources/VaporAPNS/Request+APNS.swift](https://app.codecov.io/gh/vapor/apns/pull/57?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9WYXBvckFQTlMvUmVxdWVzdCtBUE5TLnN3aWZ0) | `100.00% <ø> (ø)` | | | [Sources/VaporAPNS/APNSContainers.swift](https://app.codecov.io/gh/vapor/apns/pull/57?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9WYXBvckFQTlMvQVBOU0NvbnRhaW5lcnMuc3dpZnQ=) | `87.17% <84.00%> (+0.51%)` | :arrow_up: |

[ffried]

@0xTim Done

[0xTim]

@ffried Finally can you update the test workflow - I think the reusable workflow branch has been merged so you can point to main now (like Vapor again)

[ffried]

@0xTim Also done

[0xTim]

Thanks, we're good to go!

[kylebrowning]

Thanks Team!