[locator] add open form action, automatically open form for non geometric layers

[3nids]

instead of showing of warning

This is for the "Active Layer Locator Filter".

I consider this as a bugfix as it replicates what is done in the other similar filter: "All Layers".

[qgis-bot]

The backport to release-3_16 failed:

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

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_16 release-3_16
# Navigate to the new working tree
cd .worktrees/backport-release-3_16
# Create a new branch
git switch --create backport-43462-to-release-3_16
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick e87435cc9e4751b8da13f62d470fd68c318d2af8,5f3d7757ad768f38b394b3939a81a670b3c8bcab,5b8c3dd9b68f605b4272af1573db60b1bc323c3c
# Push it to GitHub
git push --set-upstream origin backport-43462-to-release-3_16
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-3_16

Then, create a pull request where the base branch is release-3_16 and the compare/head branch is backport-43462-to-release-3_16.