Homography GCP transformer: fix bad scaling factor on overviews (3.11.0 regression)

[rouault]

Fixes qgis/QGIS#65011

[rouault]

The backport to release/3.12 failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply 54b218695e... Homography GCP transformer: fix bad scaling factor on overviews (3.11.0 regression)
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config set advice.mergeConflict false"

stdout

Auto-merging alg/gdal_homography.cpp
Auto-merging autotest/alg/warp.py
CONFLICT (content): Merge conflict in autotest/alg/warp.py

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-release/3.12 release/3.12
# Navigate to the new working tree
cd .worktrees/backport-release/3.12
# Create a new branch
git switch --create backport-13968-to-release/3.12
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 54b218695e101f7c9a211098ad0dbb46a6e142d4
# Push it to GitHub
git push --set-upstream origin backport-13968-to-release/3.12
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release/3.12

Then, create a pull request where the base branch is release/3.12 and the compare/head branch is backport-13968-to-release/3.12.

[rouault]

backported to 3.12 per 9e8dec4