hevm: decode ds-note events

[ds-note](https://github.com/dapphub/ds-note) emits anonymous events, which show up in the trace output as

```
├╴ 0x... [data] ... (src/note.sol:39)
```

where `[data]` is the binary from the (un-indexed) event args. This data includes the full calldata, which could be decoded and shown, given that the first argument to the `note` event is `msg.sig`, allowing the function abi to be looked up in the `abiMap`.

```
event LogNote(bytes4 indexed, address indexed, bytes32 indexed, bytes32 indexed, uint256, bytes) anonymous;

modifier note {
bytes32 foo;
bytes32 bar;
uint256 wad;

assembly {
foo := calldataload(4)
bar := calldataload(36)
wad := callvalue
}

emit LogNote(msg.sig, msg.sender, foo, bar, wad, msg.data);

_;
}
```