Move Args.cpp from Interpreter to Utility

Summary:
The Args class is used in plenty of places besides the command
interpreter (e.g., anything requiring an argc+argv combo, such as when
launching a process), so it needs to be in a lower layer. Now that the
class has no external dependencies, it can be moved down to the Utility
module.

This removes the last (direct) dependency from the Host module to
Interpreter, so I remove the Interpreter module from Host's dependency
list.

Reviewers: zturner, jingham, davide

Subscribers: mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D45480

llvm-svn: 330200