Improve --checklist output with ID and Impact/Confidence

Currently the `--checklist` outputs markdown as follows:

---

## arbitrary-send

| Analyzed | Description |
|----------------|-----------|
|

• [ ] TP
• [ ] FP
• [ ] Unknown

• SomeContract._someFn(uint256) (contracts/SomeContract.sol#11-12) sends eth to arbitrary user
  • Dangerous calls:
    • - (success) = msg.sender.call{value: someValue}() (contracts/SomeContract.sol#12)
      |
      • [ ] TP
      • [ ] FP
      • [ ] Unknown
      |
      • SomeOtherContract._someOtherFn(uint256) (contracts/SomeOtherContract.sol#74-79) sends eth to arbitrary user
        • Dangerous calls:
          • - (success) = msg.sender.call{value: _amount}() (contracts/SomeOtherContract.sol#78)

            ---

            It would be really useful if the following improvements were made to this output:
            - Give each slither finding an ID (start at 1, increment). This would allow to easily refer to a specific finding when communicating these slither results. For example, you could then say: "Opened issue #999 for slither finding 2", or "Could you take a look at slither finding 14, I'm not too sure about it"
            - add Impact and Confidence to each finding

            ---

            This might break other projects that use the `--checklist` and somehow integrate/parse it.