Dedupe MSRC downloads/deletes when enrolled hosts include multiple builds of the same version of Windows

[iansltx]

For #25090.

Checklist for submitter

If some of the following don't apply, delete the relevant line.

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.
• Input data is properly validated, SELECT * is avoided, SQL injection is prevented (using placeholders for values in statements)
• Added/updated automated tests
• A detailed QA plan exists on the associated ticket (if it isn't there, work with the product group's QA engineer to add it)
• Manual QA for all new/changed functionality

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.99%. Comparing base (56f6349) to head (9926bc6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #27060      +/-   ##
==========================================
- Coverage   64.00%   63.99%   -0.01%     
==========================================
  Files        1706     1706              
  Lines      162934   162942       +8     
  Branches     4310     4310              
==========================================
- Hits       104283   104279       -4     
- Misses      50529    50537       +8     
- Partials     8122     8126       +4     

Flag	Coverage Δ
backend	64.76% <100.00%> (-0.01%)	⬇️

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