Groovy Hooks may run before or after JOB_CONFIG_ADAPTED

After introduction a new milestones in the core,  Groovy hooks may run before or after JOB_CONFIG_ADAPTED depending on how graph is executed. We need to apply a fix in the Jenkins core to ensure that JCasC and Groovy Hooks still interact in a predictable way.

Proposal:

• Revert https://github.com/jenkinsci/jenkins/commit/ab12f71a48901ab3b78521382057a03e166fe668 to the orifginal state so that init hook behaves as before: after all initialization steps
• Document Groovy Hooks and explicitly document the state
• Consider introducing new hooks for specific items like post-job-initialization