[FEATURE] Enable filename of fileResults in track egressInfo

[momenthana]

Is your feature request related to a problem? Please describe.
Just as the fileResults filename comes in at event "egress_started" in egressInfo, where the request case is "roomComposite", the track should also be provided to ensure power and consistency in the webhook.

If egress_started and roomComposite, the filename is returned from the results and fileResults.

{
  "id": "EV_8oTjKXHjCqyD",
  "event": "egress_started",
  "createdAt": {
    "$numberLong": "1736317932"
  },
  "egressInfo": {
    "egressId": "EG_ybxRsSGKD5vY",
    "roomId": "RM_7A62FjVFwWw5",
    "roomName": "3d0e0a0b-aa63-49b2-8724-8ecefc0d3b5c",
    "request": {
      "case": "roomComposite",
      "value": {
        "roomName": "3d0e0a0b-aa63-49b2-8724-8ecefc0d3b5c",
        "layout": "",
        "audioOnly": true,
        "videoOnly": false,
        "customBaseUrl": "",
        "output": {
          "case": "file",
          "value": {
            "fileType": 0,
            "filepath": "/d/1e/records/audios/{room_name}/{time}/audio",
            "disableManifest": false,
          }
        },
        "options": {
          "case": null
        },
        "fileOutputs": [
          {
            "fileType": 0,
            "filepath": "/d/1e/records/audios/{room_name}/{time}/audio",
            "disableManifest": false,
            "output": {
              "case": "s3",
              "value": {
                ...
              }
            }
          }
        ],
        "streamOutputs": [],
        "segmentOutputs": [],
        "imageOutputs": []
      }
    },
    "result": {
      "case": "file",
      "value": {
        "filename": "/d/1e/records/audios/3d0e0a0b-aa63-49b2-8724-8ecefc0d3b5c/2025-01-08T063212/audio.ogg",
        "startedAt": {
          "$numberLong": "0"
        },
        "endedAt": {
          "$numberLong": "0"
        },
        "duration": {
          "$numberLong": "0"
        },
        "size": {
          "$numberLong": "0"
        },
        "location": ""
      }
    },
    "streamResults": [],
    "fileResults": [
      {
        "filename": "/d/1e/records/audios/3d0e0a0b-aa63-49b2-8724-8ecefc0d3b5c/2025-01-08T063212/audio.ogg",
        "startedAt": {
          "$numberLong": "0"
        },
        "endedAt": {
          "$numberLong": "0"
        },
        "duration": {
          "$numberLong": "0"
        },
        "size": {
          "$numberLong": "0"
        },
        "location": ""
      }
    ],
    "segmentResults": [],
    "imageResults": []
  },
}

Describe the solution you'd like

Filename is not displayed when egress_started and track. Empty string.

{
  "id": "EV_YBPVozjWqJvK",
  "event": "egress_started",
  "egressInfo": {
    "egressId": "EG_XuQ4pWbSUmWh",
    "roomId": "RM_Sp8xj2Ze4sdz",
    "roomName": "aa7adbc7-2645-462e-8c6b-30c2914e5342",
    "status": 0,
    "startedAt": {
      "$numberLong": "0"
    },
    "endedAt": {
      "$numberLong": "0"
    },
    "updatedAt": {
      "$numberLong": "1736317954328690922"
    },
    "details": "",
    "error": "",
    "errorCode": 0,
    "request": {
      "case": "track",
      "value": {
        "roomName": "aa7adbc7-2645-462e-8c6b-30c2914e5342",
        "trackId": "TR_AMQhSNaGRKhh5t",
        "output": {
          "case": "file",
          "value": {
            "filepath": "/d/1e/tracks/{track_type}s/{room_name}/{publisher_identity}/{time}/{track_type}",
            "disableManifest": false,
            "output": {
              "case": "s3",
              "value": {
                ...
              }
            }
          }
        }
      }
    },
    "result": {
      "case": "file",
      "value": {
        "filename": "",
        "startedAt": {
          "$numberLong": "0"
        },
        "endedAt": {
          "$numberLong": "0"
        },
        "duration": {
          "$numberLong": "0"
        },
        "size": {
          "$numberLong": "0"
        },
        "location": ""
      }
    },
    "streamResults": [],
    "fileResults": [
      {
        "filename": "",
        "startedAt": {
          "$numberLong": "0"
        },
        "endedAt": {
          "$numberLong": "0"
        },
        "duration": {
          "$numberLong": "0"
        },
        "size": {
          "$numberLong": "0"
        },
        "location": ""
      }
    ],
    "segmentResults": [],
    "imageResults": []
  },
}

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
livekit version is 1.8.0
egress version is 1.8.6