Upgrade to GDAL 3.8.5, future-proof for 3.9.0 (use venvs)

[dmannarino]

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• Bugfix
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What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this introduce a breaking change?

• Yes
• No

Other information

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.95%. Comparing base (306fcf9) to head (8ef1b3f).

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Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #540   +/-   ##
========================================
  Coverage    81.95%   81.95%           
========================================
  Files          126      126           
  Lines         5685     5685           
========================================
  Hits          4659     4659           
  Misses        1026     1026           

Flag	Coverage Δ
unittests	81.95% <ø> (ø)

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[danscales]

Looks good, given that it all works in testing!