Provide extended allocators interface (e.g. grow/realloc) like Boost.Container

[Boost.Container allocators support extra interfaces than the standard allocator requirements](https://www.boost.org/doc/libs/1_73_0/doc/html/container/extended_allocators.html).

Some of these functions are useful even to C libraries that used to enjoy `realloc()` like features. So this extra interface is useful even if we're not planning to use it with standard containers.

It'd be nice if Boost.Interprocess could provide a few of these features for its [allocators](https://www.boost.org/doc/libs/1_73_0/doc/html/interprocess/allocators_containers.html) as [`managed_shared_memory`](https://www.boost.org/doc/libs/1_73_0/doc/html/interprocess/managed_memory_segments.html#interprocess.managed_memory_segments.managed_memory_segment_features.allocate_deallocate) has plenty of features not found in Boost.Container allocators and we cannot use Boost.Container extended allocators to manage preallocated memory regions.

Empieza leyendo la documentación enlazada sobre los allocators extendidos de Boost.Container y compárala después con la documentación del allocator y de managed_shared_memory de Boost.Interprocess. Identifica qué operaciones del allocator pueden admitirse para regiones de memoria preasignadas y define la interfaz y las pruebas necesarias. Se considera completado cuando las operaciones extendidas seleccionadas están disponibles mediante los allocators de Boost.Interprocess sin depender de los requisitos de los contenedores estándar.

Escrito por el modelo de indexación a partir del texto del issue.