Update [email protected] (#44)

Fix another instance of

```
'swift-clocks': /__w/SwiftPackageIndex-Server/SwiftPackageIndex-Server/.build/checkouts/swift-clocks/[email protected]:5:15: warning: 'init(name:defaultLocalization:platforms:pkgConfig:providers:products:dependencies:targets:swiftLanguageVersions:cLanguageStandard:cxxLanguageStandard:)' is deprecated: replaced by 'init(name:defaultLocalization:platforms:pkgConfig:providers:products:dependencies:targets:swiftLanguageModes:cLanguageStandard:cxxLanguageStandard:)'
```

Make AnyClock a class. (#41)

Weirdly `AnyClock` crashes on Wasm when it's a struct, but as a class it
works. Luckily it's fine to make it a class.

Point Issue Reporting to xctest-dynamic-overlay repo (#40)

Swift Package Manager honors redirects, but it appears to associate the
path suffix with the package name, and this conflicts with package
resolution in certain (but not all) cases.

I think we have no choice but to roll back everything to point to the
original xctest-dynamic-overlay URL and extract Issue Reporting to a
dedicated repo.

Add support for Swift Testing (#39)

Makes it so `TestClock` and `UnimplementedClock` both report failures to
the new Swift Testing framework.

---------

Co-authored-by: Brandon Williams <[email protected]>

Fix regression: test clock should hang till it is explicitly advanced (…

…#26)

We merged #22 a bit too hastily, but it introduced behavior that we
didn't actually want. Let's revert this behavior and get a test in place
so we don't deviate in the future.

Remove AsyncAlgorithms (#25)

throttle -> _throttle
Remove select

Bump dependencies

Depend on ConcurrencyExtras (#21)

We use `Task.megaYield` to make Swift concurrency more reliable, so
let's bring it in from a shared library.

Add mega yield environment variable (#18)

An idea suggested
[here](pointfreeco/combine-schedulers#79).
Because we reuse `Task.megaYield` in Clocks, Combine Schedulers, and
TCA, we can use an environment variable to unify them.

Expose concrete `AnyClock` type (#11)

There are limitations in Swift that prevent existential clocks (_e.g._
`any Clock<Duration>`) from being used in certain APIs, like those
provided by the Async Algorithms package. To work around this, we should
ship a concrete eraser that can be used where existentials cannot.

Co-authored-by: Brandon Williams <[email protected]>