ci: librarian checks should indicate steps to repair

[westarle]

When the tidy or generate checks fail, it isn't perfectly clear how to recover. Mainly, the version check isn't obvious:

Regeneration failed. Please run 'librarian generate --all' to update the generated files.

Ideally this is a (very short) script we run like ci/librarian

# Get the librarian version currently used in node
V=$(go run github.com/googleapis/librarian/cmd/librarian@latest config get version)

# format librarian.yaml file
go run github.com/googleapis/librarian/cmd/librarian@${V}  tidy

# install all node dependencies specified in librarian.yaml
go run github.com/googleapis/librarian/cmd/librarian@${V} install

# run generate to apply all changes to repo-metadata
go run github.com/googleapis/librarian/cmd/librarian@${V} generate --all

Originally posted by @quirogas in #9145 (comment)