Fix unneeded rescan when importing transactions in chunk

[Alenar]

Content

This PR fix the issue described in #2021.

To do so the way that the importer obtains its starting point change:

• Before it would compute it by getting data from the highest stored transactions in database, this caused the issue since in test networks there may be huge ranges of blocks without transactions.
• Now if keep stored the last ChainPoint that was polled by its block streamer after each import, so it can be used as the next import start point, solving the issue.

Curated logs from the e2e before the change

The same start block number is used repeatedly

{ "msg": "Retrieving Cardano transactions between block_number '0' and '150'" }
{ "msg": "Retrieving Cardano transactions between block_number '0' and '300'" }
{ "msg": "Retrieving Cardano transactions between block_number '254' and '419'" }
{ "msg": "Retrieving Cardano transactions between block_number '341' and '434'" }
{ "msg": "Retrieving Cardano transactions between block_number '341' and '449'" }
{ "msg": "Retrieving Cardano transactions between block_number '341' and '449'" }
{ "msg": "Retrieving Cardano transactions between block_number '341' and '464'" }

Curated logs from the e2e after the change

No start block number is used more than once

{ "msg": "Retrieving Cardano transactions between block_number '0' and '150'" }
{ "msg": "Retrieving Cardano transactions between block_number '150' and '300'" }
{ "msg": "Retrieving Cardano transactions between block_number '300' and '450'" }
{ "msg": "Retrieving Cardano transactions between block_number '450' and '569'" }
{ "msg": "Retrieving Cardano transactions between block_number '569' and '584'" }
{ "msg": "Retrieving Cardano transactions between block_number '584' and '599'" }
{ "msg": "Retrieving Cardano transactions between block_number '599' and '614'" }

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested

Issue(s)

Closes #2021

[github-actions]

Test Results

    4 files  ± 0     55 suites  ±0   10m 41s ⏱️ +19s
1 393 tests +14  1 393 ✅ +14  0 💤 ±0  0 ❌ ±0 
1 607 runs  +14  1 607 ✅ +14  0 💤 ±0  0 ❌ ±0 

Results for commit 84ca63f. ± Comparison against base commit af96205.

♻️ This comment has been updated with latest results.

[jpraynaud]

LGTM 👍