Adopt `Sendable` in `NIOEmbedded` (#2195)
Adopt `Sendable` in `NIOEmbedded` (#2195)

`EmbeddedChannel` and `EmbeddedEventLoop` should not be `Sendable`. However, they inherit from `Channel` and `EventLoop` respectively. Therfore, they need to be `Sendable` (and are already implcitily `Sendable`. Given these constraints, we can’t mark `EmbeddedChannel` and `EmbeddedEventLoop` as non-Sendable.
apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio