Split out cancel_build from update_build

What does this MR do and why?

The behavior of the application stays the same while splitting cancel_build from update_bulid. With the minor change of the added graphql field which will be used when the frontend is developed.

This is in preparation for preventing cancel_build for certain roles based on a new setting.

That will allow us to add this code:

!135047 (diffs)

      rule { ci_cancellation_maintainers_only & ~can?(:maintainer_access) }.policy do
        prevent :cancel_pipeline
        prevent :cancel_build
      end

      rule { ci_cancellation_no_one }.policy do
        prevent :cancel_pipeline
        prevent :cancel_build
      end

Related to #20207 (closed)