Make it easier to spin up multiple similar client pairs

[barnabasbusa]

It would also be great if we could have a new participant field where we could have a new variable called count, where we could define we need 5 ligthhouse-geth pairs for example, and it would spin that up, without needing to define it 5 times the same thing.

so instead of using:

{
  "participants": [
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
    },

one could use

{
  "participants": [
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
      "count" : 5
    },

More examples:

{
  "participants": [
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "lighthouse",
      "cl_client_image": "ethpandaops/lighthouse:boxed-blobs-d534ac0"
      "count": 5
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "teku",
      "cl_client_image": "consensys/teku:develop"
      "count": 2
    },
    {
      "el_client_type": "geth",
      "el_client_image": "ethpandaops/geth:4844-devnet-6-e03b5ad",
      "cl_client_type": "nimbus",
      "cl_client_image": "consensys/teku:develop"
    }
  ],
  "network_params": {
    "deneb_fork_epoch": 3
  },
  "launch_additional_services": true,
  "wait_for_finalization": false,
  "wait_for_verifications": false,
  "global_client_log_level": "info"
}

Would create the following pairs:

geth-lighthouse-0, lighthouse-geth-0, lighthouse-geth-validator-0
geth-lighthouse-1 ...
...
geth-lighthouse-4, lighthouse-geth-4, lighthouse-geth-validator-4
geth-teku-0, teku-geth-0
geth-teku-1, teku-geth-1
geth-nimbus-0, nimbus-geth-0