fix: Add version check in basicTxn.Query

[fredcarle]

Relevant issue(s)

Resolves #2741

Description

This PR fixes a bug with the memory store where basicTxn.Query did not consider the transaction version when querying. This means that it could return KVs created after the transaction was initiated.

Note that the first commit documents the bug.

Tasks

• I made sure the code is well commented, particularly hard-to-understand areas.
• I made sure the repository-held documentation is changed accordingly.
• I made sure the pull request title adheres to the conventional commit style (the subset used in the project can be found in tools/configs/chglog/config.yml).
• I made sure to discuss its limitations such as threats to validity, vulnerability to mistake and misuse, robustness to invalidation of assumptions, resource requirements, ...

How has this been tested?

make test

Specify the platform(s) on which this was tested:

• MacOS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.12%. Comparing base (e3eca29) to head (9891f2a).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2742      +/-   ##
===========================================
+ Coverage    78.08%   78.12%   +0.05%     
===========================================
  Files          311      311              
  Lines        23235    23238       +3     
===========================================
+ Hits         18141    18154      +13     
+ Misses        3706     3701       -5     
+ Partials      1388     1383       -5     

Flag	Coverage Δ
all-tests	78.12% <100.00%> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
datastore/memory/txn.go	98.79% <100.00%> (+0.02%)	⬆️

... and 6 files with indirect coverage changes

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[nasdf]

LGTM. Thanks for tracking this down!