Update sonic-utilities to support new SKU Mellanox-SN5600-O128

[stephenxs]

What I did

Update sonic-utilities to support new SKU Mellanox-SN5600-O128

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

How I did it

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)