Single threaded OakMap

[sanastas]

Add a flag to Oak, such that if turned on, OakMap is optimized for a single thread performance.

A flag should be added to OakBuilder to signal of creating an OakMap to be used by single thread. The flag should propagate to the internal Oak usage of CAS, where the later should be wrapped and based on the flag either CAS or simple write should be used.

The issue is not very complex but still requires understanding of OakMap design and internal classes structure. In addition to the running and correct version of single threaded Oak, the outcome of the issue should also be Oak benchmarks showing performance of single- versus multi-threaded OakMap.

For more explanations feel free to add questions in this issue.