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]

Codecov Report

All modified and coverable lines are covered by tests ✅

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

Additional details and impacted files

@@            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)