This ticket is the mongo-tools equivalent of REP-6040.

To support the goal of 100% specified code-ownership, we need to have the tooling from the mongo repo which generates a top-level .github/CODEOWNERS file from per-directory OWNERS.yml files.

This should be implemented in mongo-tools roughly the same way as in mongosync - e.g. copy the mongosync scripts which are under mongosync/owners. But there will be slight differences in the way it integrates with the build system because mongosync uses mage.go and mongo-tools are different.

Also mongosync uses mise to install binary tools, including the "codeowners" and "codeowners-validator" executables, but up to now we haven't used mise in mongo-tools so either we need to start using mise, or install those some other way.