Support RDMA bandwidth calculation for heterogeneous GPU server configurations

[alpha-baby]

Problem Background

The existing implementation of get_rdma_gbs() returned only the bandwidth of a single RDMA NIC. This leads to inaccurate bandwidth calculations in the following heterogeneous server configurations:

1. GPU-NIC Mismatch: Some server configurations have multiple GPUs sharing fewer RDMA NICs (e.g., 8 GPUs sharing 4 RDMA NICs instead of 1:1 ratio)
2. NIC Bonding Configuration: Certain network architectures use 802.3ad LACP bonding to aggregate multiple physical NICs into a single logical interface thx @michaelchen1996 RP:Try to detect 802.3ad LACP bonding slaves and multiply by slave count #618

Key Behavioral Changes

Before:

return rate / 8  # Returns single NIC bandwidth only

After:

nic_count = _get_active_rdma_nic_count(output, nic_name)
# Detects bonding and multiplies by slave count...
gpu_count = _get_local_gpu_count()
return rate * nic_count / gpu_count / 8  # Returns per-GPU allocated bandwidth

Compatibility

• For standard 1 GPU : 1 NIC configurations, the calculation result remains the same as before
• For multi-GPU shared NIC scenarios, now correctly reflects the actual RDMA bandwidth available to each GPU
• Function signature remains unchanged, fully backward compatible