fix(indexes): Fix wrong order in MemoryTxGroupIndex

[msbrogli]

Motivation

MemoryTxGroupIndex._get_sorted_from_key() is returning transactions in the wrong order. The correct order is sorted by (timestamp, hash) but it is actually only sorting by hash.

Acceptance Criteria

1. Replace set[bytes] to set[tuple[int, bytes]] so we can simply sort before returning the results.
2. Fix _get_sorted_from_key() sorting the tuple but returning only the hashes.

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 ✅

Project coverage is 85.15%. Comparing base (4ccc883) to head (8aa43a7).

❗ Current head 8aa43a7 differs from pull request most recent head d3511d4. Consider uploading reports for the commit d3511d4 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #977      +/-   ##
==========================================
+ Coverage   85.13%   85.15%   +0.02%     
==========================================
  Files         294      294              
  Lines       22781    22782       +1     
  Branches     3426     3428       +2     
==========================================
+ Hits        19395    19401       +6     
+ Misses       2706     2701       -5     
  Partials      680      680              

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