Fix SIP issue with return results from calculateStatistics

[elpaso]

Fixes #43245

SIP failed to convert the QMap<QgsZonalStatistics::Statistic, QVariant>
so we give it an QMap<int, QVariant>.

[qgis-bot]

The backport to queued_ltr_backports failed:

The process '/usr/bin/git' failed with exit code 128

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-queued_ltr_backports queued_ltr_backports
# Navigate to the new working tree
cd .worktrees/backport-queued_ltr_backports
# Create a new branch
git switch --create backport-43332-to-queued_ltr_backports
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick b1f631e69606ad9c9d20929736add9e26a4f31b4
# Push it to GitHub
git push --set-upstream origin backport-43332-to-queued_ltr_backports
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-queued_ltr_backports

Then, create a pull request where the base branch is queued_ltr_backports and the compare/head branch is backport-43332-to-queued_ltr_backports.