Add more info about why lookup is in AwaitingDownload

[dapplion]

Issue Addressed

When debugging lookup stuck incidents in https://github.com/sigp/lighthouse/issues/5833, it's very helpful to know if the specific reason why a lookup is at the AwaitingDownload state.

Proposed Changes

As purely informational, append to AwaitingDownload enum variant the last reason why the lookup is at that state.

[realbigsean]

@mergify queue

[mergify[bot]]

queue

🛑 The pull request has been removed from the queue default

The pull request conflicts with at least one pull request ahead in queue.

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[michaelsproul]

needs an update

[jimmygchen]

@mergify queue

[mergify[bot]]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 6a7305a4876810ad64eda62686077247c1f9947c