Scraper should not miss events

[ameten]

Problem

Is your feature request related to a problem? Please describe.
Currently Scraper can miss a delivery message event when it cannot ensure that a block or a transaction are stored into database. It happens in the cases, for example, when RPC is not functional and Scraper cannot request a block or a transaction.

Additional context
It happens only in Scraper since Validator is only indexing MerkleTreeInsertion (always sequance-aware) and Relayer is indexing HyperlaneMessages (sequence-aware), MerkleTreeInsertions (sequence-aware) and InterchainGasPayments (watermark-aware but with back channel from HyperlaneMessages).

Solution

Describe the solution you'd like
Scraper should not advance its cursors if some of the logs are not indexed for any reason.