ci: Use new Debian Trixie images

[bthomee]

High Level Overview of Change

This change uses the new Debian Trixie CI images added by XRPLF/ci#83.

Context of Change

Debian 13 ("Trixie") was released several months ago, and can now be used to build and test with.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.6%. Comparing base (2c18746) to head (fb4ab8b).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6034   +/-   ##
=======================================
  Coverage     78.6%   78.6%           
=======================================
  Files          817     817           
  Lines        68976   68976           
  Branches      8245    8244    -1     
=======================================
+ Hits         54189   54191    +2     
+ Misses       14787   14785    -2     

see 2 files with indirect coverage changes

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[bthomee]

In a previous commit I ran builds and tests with the new images. As with Bookworm, the Clang builds failed on ARM64, so I updated the strategy matrix generation script to exclude Clang 21 as well. The new images will be used during the nightly runs.