Use apr_palloc/apr_pmemdup rather than malloc/memcpy in mod_tile.c

[hummeltech]

Also:

• Add HEAD request test
• Add renderd_config_test helper
• Improve renderd_config testing
• Consolidate redundant code in mod_tile.c
• Stop unnecessarily reading renderd.conf 3 times
• Don't try to build CentOS Stream 9/10 until gdal RPM issue is resolved
  • https://issues.redhat.com/browse/RHEL-134116

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 97.34513% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.78%. Comparing base (c4e3e62) to head (8e311e9).
⚠️ Report is 24 commits behind head on master.

Files with missing lines	Patch %	Lines
src/mod_tile.c	95.52%	3 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #491      +/-   ##
==========================================
- Coverage   81.54%   80.78%   -0.76%     
==========================================
  Files          24       24              
  Lines        5645     5215     -430     
==========================================
- Hits         4603     4213     -390     
+ Misses       1042     1002      -40     

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