Move Onboarding Progress construct/updating to `ee` from `ce`

Currently the onboarding_progresses table is only ever used/consumed on Gitlab.com in Learn GitLab.

This means we should move the updating and code from this table onboarding_progresses

Plan

See https://docs.gitlab.com/ee/development/ee_features.html for help here

• Move all uses of Onboarding::ProgressService to ee.
• Move Onboarding::ProgressService to ee. Be aware of any async cases that could be invoked here.
• Move all uses of Onboarding::Progress to ee.
• Move Onboarding::Progress to ee.
• Final look-around/cleanup.

original description

The following discussion from !149617 (merged) should be addressed:

• @dstull started a discussion:

  thought (non-blocking):

  Onboarding and observing it in learn gitlab is a fully Gitlab.com only concept. We should explore moving the whole onboarding progress concept to ee.