fix(anvil): refetch full fork blocks with missing tx cache

[solanaXpeter]

Motivation

Cached fork blocks can lose one or more stored transaction payloads while still keeping the block shell. When block_by_hash_full or block_by_number_full reconstructs that stale cache entry, RPC consumers receive an incomplete full block instead of a refetched upstream response.

Solution

Return None from full-block reconstruction when any cached transaction is missing, then fall back to fetch_full_block(...) so the fork cache is repaired from upstream data. Add an integration test that removes one cached transaction and asserts the next full-block read refetches and restores it.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[figtracer]

this is defensive but not sure how important it is here, pending another review

[mattsse]

doesnt hurt

[solanaXpeter]

Hi @mattsse, thanks for your review. I noticed this was approved and later closed while I was working on the CI issue, so I wanted to check whether there was some other concern with the change.

[mablr]

re-opened 👍

[solanaXpeter]

@mablr @mattsse @figtracer I fixed the CI issue. Could you please re-run the CI? Thanks very much for your time!