Move __tsan::Vector to __sanitizer

Summary:
The low-fat STL-like vector container will be reused in MSan.

It is needed to implement an atexit(3) interceptor on NetBSD/amd64 in MSan.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, dvyukov, eugenis, vitalybuka, kcc

Reviewed By: dvyukov

Subscribers: kubamracek, mgorny, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D40726

llvm-svn: 319650