feat(p2p): remove availability checks from retriever

[srene]

PR Standards

This PR removes the availability checks from the retriever, since it requires additional syncing with DA and availability checks are not really necessary at this point where sequencers are trusted and fraud proofs are not enabled yet in full-nodes.

Opening a pull request should be able to meet the following requirements

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Close #834

<-- Briefly describe the content of this pull request -->

For Author:

• [ ] Targeted PR against correct branch
• [ ] included the correct type prefix in the PR title
• [ ] Linked to Github issue with discussion and accepted design
• [ ] Targets only one github issue
• [ ] Wrote unit and integration tests
• [ ] All CI checks have passed
• [ ] Added relevant godoc comments

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For Reviewer:

• [ ] confirmed the correct type prefix in the PR title
• [ ] Reviewers assigned
• [ ] confirmed all author checklist items have been addressed

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After reviewer approval:

• [ ] In case targets main branch, PR should be squashed and merged.
• [ ] In case PR targets a release branch, PR should be rebased.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 40.40%. Comparing base (851b312) to head (aab2158). Report is 8 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #835 +/- ## ========================================== - Coverage 40.44% 40.40% -0.05% ========================================== Files 120 119 -1 Lines 18935 18868 -67 ========================================== - Hits 7659 7623 -36 + Misses 10201 10170 -31 Partials 1075 1075 ```

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[mtsitrin]

I'm fine to merge it, but to notice, it affects not only full nodes but also a sequencer that needs to be synced initially (in syncBlockManager function)