[Windows] Fix threads comparison on Windows

Summary:
This patch makes Windows threads to compare by a thread ID, not by a handle.
It's because the same thread can have different handles on Windows
(for example, `GetCurrentThread` always returns the fake handle `-2`).
This leads to some incorrect behavior. For example, in `Process::GetRunLock`
always `m_public_run_lock` is returned without this patch.

Reviewers: zturner, clayborg, stella.stamenova

Reviewed By: stella.stamenova

Subscribers: stella.stamenova, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D53357

llvm-svn: 344729