[lldb-server] Add remote platform capabilities for Windows

Summary:
Implement a few routines for Windows to support some basic process interaction and file system operations.

Reviewers: zturner, llvm-commits, labath, jingham

Reviewed By: labath

Subscribers: emaste, jdoerfert, Hui, labath, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D56232