[Windows] A basic implementation of memory allocations in a debuggee process

Summary:
This patch adds a basic implementation of `DoAllocateMemory` and
`DoDeallocateMemory` for Windows processes. For now it considers only the
executable permission (and always allows reads and writes).

Reviewers: zturner, asmith, stella.stamenova, labath, clayborg

Reviewed By: zturner

Subscribers: Hui, vsk, jingham, aleksandr.urakov, clayborg, abidh, teemperor, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D52618

llvm-svn: 345815