perf: optimize trace decoding by making identity fetching non-blocking

### Component

Forge

### Describe the feature you would like

Ref #3006

Decoding traces for better output can make use of etherscan or sig.eth.samczsun.com

both require API requests, the tracing decoding is currently blocking, which means we have code that looks like:

https://github.com/foundry-rs/foundry/blob/903562382075b4ba24e5f4d40aeee620c53a7dde/evm/src/trace/identifier/etherscan.rs#L86

we could solve this by making everything async or use a background task with channels instead

since there's only 1 identifier for the entire suit, the latter makes sense, this way we still keep the non async test interface but can use async decoding

### Additional context

_No response_