CI: Linux: test install target, and fix installation of Python bindings on debian:unstable with py3.12

[rouault]

No description provided.

[coveralls]

coverage: 67.911% (-0.001%) from 67.912%
when pulling 248d780 on rouault:ci_install
into fe649a8 on OSGeo:master.

[rouault]

The backport to release/3.8 failed:

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

stderr

error: could not apply 8a1f0fea9d... CI: Linux: test install target
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".

stdout

Auto-merging .github/workflows/alpine/build.sh
CONFLICT (content): Merge conflict in .github/workflows/alpine/build.sh
Auto-merging .github/workflows/ubuntu_20.04/build.sh
CONFLICT (modify/delete): .github/workflows/ubuntu_22.04/build.sh deleted in HEAD and modified in 8a1f0fea9d (CI: Linux: test install target).  Version 8a1f0fea9d (CI: Linux: test install target) of .github/workflows/ubuntu_22.04/build.sh left in tree.

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/3.8 release/3.8
# Navigate to the new working tree
cd .worktrees/backport-release/3.8
# Create a new branch
git switch --create backport-8812-to-release/3.8
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 8a1f0fea9dce2e6135be9e1ba53f7898fb3baf5a,11cd5251e3166648ab51ca499468d0b144fcbfe9,248d7809a46d2fefd7fe320b434182ebe2805ca7
# Push it to GitHub
git push --set-upstream origin backport-8812-to-release/3.8
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release/3.8

Then, create a pull request where the base branch is release/3.8 and the compare/head branch is backport-8812-to-release/3.8.

[rouault]

manual backport in #8825