Fix AsyncHTTPClient Warnings and Update Package.resolved

[mgacy]

#8 updated Package.dependencies but did not include the corresponding changes to Package.resolved; this adds those changes (async-http-client now depends on swift-algorithms, which depends on swift-numerics).

Also, HTTPClient.EventLoopGroupProvider.createNew is now deprecated:

public enum EventLoopGroupProvider {
    ...
    @available(*, deprecated, renamed: "singleton", message: "Please use the singleton EventLoopGroup explicitly")
    case createNew
}

This fixes the resultant warnings by using HTTPClient.EventLoopGroupProvider.singleton as suggested.