bkpr-listincome doesn't filter `onchain_fee` income events when start_time and end_time range is provided

[ShahanaFarooqui]

Expected Behaviour:

All income events, including onchain_fee, should respect the specified time range filter.

Observed Behaviour:

onchain_fee entries are included in the results regardless of the provided start_time and end_time constraints.

Example Request:

lightning-cli bkpr-listincome -k start_time=1743445800 end_time=1746037799

Example Response:

{
   "income_events": [
      {
         "account": "0fbcaf5930c7e5dfc89feec2fd8a3e0ed8f9a8ce76f62a4e334e74c33828683c",
         "tag": "onchain_fee",
         "credit_msat": 0,
         "debit_msat": 166000,
         "currency": "bcrt",
         "timestamp": *1738463349,
         "txid": "3c682838c3744e334e2af676cea8f9d80e3e8afdc2ee9fc8dfe5c73059afbc0f"
      },
      {
         "account": "53b44f8d56882fe297f8f2e5f7bf5ee4709512ea0acf13f3282c08266f773a2c",
         "tag": "onchain_fee",
         "credit_msat": 0,
         "debit_msat": 166000,
         "currency": "bcrt",
         "timestamp": *1738463349,
         "txid": "2c3a776f26082c28f313cf0aea129570e45ebff7e5f2f897e22f88568d4fb453"
      },
      {
         "account": "f97b51ffb55cd0761370cacb493da425b232d48012516fc2468222ffdee5c949",
         "tag": "routed",
         "credit_msat": 23,
         "debit_msat": 0,
         "currency": "bcrt",
         "timestamp": 1743542350,
         "payment_id": "9a0a1c8ecaba7ff487ea96c9e2e96636482b3f6b2844f35d4c51d283060ca2b2"
      },
     ...
    ]
}