`v6` Rollout

[CodeGat]

References PR #306

Background

This issue serves as a progress-tracker for rolling out the new major version build-cd v6.

Generally, the changes for MDRs:

• In the manifest: The spack.modules section is no longer required as it is injected at build-time. Users can still override it.
• In the workflow: There are now new, required inputs: spack-manifest-schema-version, config-versions-schema-version and config-packages-schema-version. There is also a new, optional input spack-manifest-schema-path that defaults to the usual schema.
• There is a new config/packages.json file that specifies special packages - ones for the release database, and another for module includes
• There is a new .github/CODEOWNERS file that means any modification to .github needs to be reviewed by @CodeGat. It can be overridden by repository admins.
• We can delete vars.*_SCHEMA_VERSION, vars.BUILD_DB_PACKAGES once this is merged.

Note

Don't forget to do model-tools, system-tools, model-deployment-template, software-deployment-template specially!