Make ignoring duplicates `PackageTemplate` claims more robust

Make ignoring duplicates `PackageTemplate` claims more robust

`update_claims_view_from_requests` assumes that any
`PackageTemplate`s passed to it will not be aggregated (i.e. have
only one input) and uses that assumption when skipping duplicates.

This is currently true, but dropping `PackateTemplate` claims
entirely based on only the first input is somewhat brittle so we
add a debug assertion here and update the logic to not spuriously
drop claims if they happen to come into the `OnChainTxHandler`
pre-aggregated.