Support coalesced collectives in comm replay

[shengf-nv]

Charka comm replay missed three coalesced collectives: allgather_into_tensor_coalesced, reduce_scatter_tensor_coalesced, allreduce_coalesced. These collectives are being used in Megatron Llama4. This PR is to add the support of these collectives in comm replay.

I also cleaned up some code in allocating tensors for collectives. Some ops will double allocate the tensors.

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