[202405][Mellanox] Add new SKU Mellanox-SN5600-C256

[DavidZagury]

What I did

A cherry-pick of https://github.com/sonic-net/sonic-utilities/pull/3431

How I did it

Update sonic-utilities to support new SKU Mellanox-SN5600-C256

Add the SKU to the generic configuration updater Simplify the logic of the buffer migrator to support the new SKU

How to verify it

Manual and unit tests

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)