fix(verification): avoid validation downgrade by not running it twice

[jansegre]

Motivation

In new sync-v2 sync flow, a node can receive a transaction that it already has, but the node might run validate_basic before processing the transaction. Before this PR running validate_basic on an existing and fully verified transaction would run the validation and downgrade the validation state from FULL to BASIC.

Acceptance Criteria

• Adjust both validate_basic to skip the validation if the given transaction has already been validated at the same or higher validation level.
• Adjust both validate_full to skip the validation if the given transaction has already been validated at the same or higher validation level. Removed from this PR because it affects other tests which require changes to HathorManager.on_new_tx for a proper fix and this isn't needed for anything in sync-v2

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d5be7b9) 85.36% compared to head (9f2a422) 85.32%.

❗ Current head 9f2a422 differs from pull request most recent head 27b07b1. Consider uploading reports for the commit 27b07b1 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #853      +/-   ##
==========================================
- Coverage   85.36%   85.32%   -0.05%     
==========================================
  Files         282      282              
  Lines       22267    22271       +4     
  Branches     3366     3368       +2     
==========================================
- Hits        19009    19003       -6     
- Misses       2592     2599       +7     
- Partials      666      669       +3     

Files	Coverage Δ
hathor/verification/verification_service.py	90.00% <100.00%> (+0.22%)	⬆️

... and 3 files with indirect coverage changes

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