Capture a missed VC error (#2436)
## Issue Addressed
Related to #2430, #2394
## Proposed Changes
As per https://github.com/sigp/lighthouse/issues/2430#issuecomment-875323615, ensure that the `ProductionValidatorClient::new` error raises a log and shuts down the VC. Also, I implemened `spawn_ignoring_error`, as per @michaelsproul's suggestion in https://github.com/sigp/lighthouse/pull/2436#issuecomment-876084419.
I got unlucky and CI picked up a [new rustsec vuln](https://rustsec.org/advisories/RUSTSEC-2021-0072). To fix this, I had to update the following crates:
- `tokio`
- `web3`
- `tokio-compat-02`
## Additional Info
NA