Added:
* Well-know Hyper-V VMIDs for parents, children, and loopback.
* VSock interop service GUID.
* `Dial()` and `DialContext()` to dial a specific Hyper-V socket at a
  known address (along with a corresponding `HvsockDialer` struct.

Bug fixes:
* Dial (and Listen) now properly initialize and set properties of their
  sockets after ConnectEx (and AcceptEx).
* The `socketError` used by `bind` was incorrect, it should be `int32(-1)`,
  not `uintptr(^0)`
* Return errors for `(*HvsockConn) SetDeadline`

Created a `sockets` package, currently only with syscalls to `Bind`,
`ConnectEx` and `GetSockName`, bypassing `syscall/windows` restrictions
on the types that can do so.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* comments and todos statements
* spelling
* removed dead code
* changed names to be more conventional
* unexported socket code
* made `(*HvsockDialer) Dial` take `Context`, removed `DialContext`
* added default `Dial` function
* rebased onto main
* cleaned up `Dial(` retry loop

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>