Remove DoAttachToProcessWithId(lldb::pid_t).

There were two versions of DoAttachToprocessWithId.  One that takes
a pid_t, and the other which takes a pid_t and a ProcessAttachInfo.
There were no callers of the former version, and all of the
implementations of this version were simply forwarding calls to
one version or the other.

llvm-svn: 237281