Support mixed strategy in NVIDIA MIG.

On Bottlerocket 1.34.0 MIG support was added for MIG_STRATEGY `single`.

**What I'd like:**
To support `mixed` strategy, which allows a node to expose a mixture of MIG device types across all of its GPUs, where single replicates the same `single` size across the GPUs available on the node.

See discussion: https://github.com/bottlerocket-os/bottlerocket/discussions/4436

**Any alternatives you've considered:**
Running multiple nodes that support MIG, with custom MIG profiles per node.

Start by reading the existing MIG_STRATEGY `single` support added in Bottlerocket 1.34.0 and the discussion in #4436. Trace how the current strategy configures devices, then determine the changes needed for `mixed` so a node can expose different MIG device types across its GPUs. Done means mixed-strategy nodes are supported and the behavior is verified.

Written by the indexing model from the issue text.