fix(util/thread): thread_specific_ptr finalization

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(util/rb_tree): use memory_pool at rb_tree, 5% performance improvement when using multiple threads

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(util/rb_tree): use memory_pool at rb_tree, 5% performance improvement when using multiple threads