Source code documentation updates (#9)

This change adds documentation to quite a few existing public types that
didn't have a blurb before.

Additionally, this fixes a couple things that I think either didn't make
sense when going to document them:
- Rename ConnectionStream to VsockConnectionStream. This type only
functions for vsock connections.
- Deletes NsLock+Closure. This was not used anywhere.
- Rename ContainerizationOCI/Config.swift to ImageConfig.swift.

Signed-off-by: Danny Canter <danny_canter@apple.com>

Sources/Containerization/Image/Image.swift

@@ -26,6 +26,7 @@ import SystemPackage
 import ContainerizationExtras
 #endif
 
+/// Type representing an OCI container image.
 public struct Image: Sendable {
 
     private let contentStore: ContentStore

Sources/Containerization/Image/InitImage.swift

@@ -18,6 +18,9 @@ import ContainerizationError
 import ContainerizationOCI
 import Foundation
 
+/// Data representing the image to use as the root filesystem for a virtual machine.
+/// Typically this image would contain the guest agent used to facilitate container
+/// workloads, as well as any extras that may be useful to have in the guest.
 public struct InitImage: Sendable {
     public var name: String { image.reference }