Sort found variables by length descending

[MagnusHJensen]

Related issue: Resolves #33502

This fixes the mentioned issue by always sorting the found variables in length descending, to ensure we process the longest variables first, avoiding us processing a smaller variation of a longer variable first breaking substitution.

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.

Testing

• Added/updated automated tests
• QA'd all new/changed functionality manually

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.14%. Comparing base (e393c1a) to head (6d623c3).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #33875      +/-   ##
==========================================
+ Coverage   64.13%   64.14%   +0.01%     
==========================================
  Files        2052     2052              
  Lines      206102   206241     +139     
  Branches     6847     6847              
==========================================
+ Hits       132183   132295     +112     
- Misses      63542    63550       +8     
- Partials    10377    10396      +19     

Flag	Coverage Δ
backend	65.27% <100.00%> (+0.01%)	⬆️

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