Error: "validate identity update failed" does not get retried when DB hits a deadlock

[mkysel]

It is possible that SelectGatewayEnvelopesByTopics throws a deadlock exception here https://github.com/xmtp/xmtpd/blob/main/pkg/indexer/app_chain/contracts/identity_update_storer.go#L289

This is a retryable error and should be handled accordingly

[mkysel]

Maybe @Maelkum's fix for #1498 will handle this case as well. Selects should not error out...