[reland][ADT] add ConcurrentHashtable class.

ConcurrentHashTable - is a resizeable concurrent hashtable.
The range of resizings is limited up to x2^31.
The hashtable allows only concurrent insertions.

Concurrent hashtable is necessary for the D96035 patch.

Reviewed By: JDevlieghere

Differential Revision: https://reviews.llvm.org/D132455