gno mod publish, and automatic loading of examples/* on gnoland's startup

[moul]

(gno mod publish or better name; publish "means smart upsert in the good order").

This tool should allow developers to don't have to think about the order of publication of a suite of packages (dependency tree).
Then, this tool should not only publish but check if the packages are already published, and at the same version.

gno mod publish --dry-run ./... could just generate the publication order to avoid chicken-egg problems.

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Bonus: call this helper from gno.land/cmd/gnoland/main.go to automatically import the whole examples/ folder instead of having a manual slice.

PS: you can start with the bonus, and create the gno mod publish for everyone, later.

[moul]

Related with #694

cc @ilgooz