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.

Start by reading the linked Boost.Container extended allocators documentation, then compare it with the Boost.Interprocess allocator and managed_shared_memory documentation. Identify which allocator operations can be supported for preallocated memory regions and define the required interface and tests. Done means the selected extended operations are available through Boost.Interprocess allocators without relying on standard container requirements.

Scritto dal modello di indicizzazione a partire dal testo della issue.