Related to JENKINS-35506

When the UI adds a new favorite to the list, it needs some data from the associated item to properly render it. It's also helpful to have the "self" href to the Favorite itself.

This ticket affects these three API's:

• https://github.com/jenkinsci/blueocean-plugin/blob/master/blueocean-rest/README.md#favorite-a-pipeline
• https://github.com/jenkinsci/blueocean-plugin/blob/master/blueocean-rest/README.md#favorite-a-multibranch-pipeline
• https://github.com/jenkinsci/blueocean-plugin/blob/master/blueocean-rest/README.md#favorite-a-multibranch-pipeline-branch

Ideally the response body for each of these requests will be a JSON representation of the favorite, in the same format as returned here (naturally only a single item, rather than array):

https://github.com/jenkinsci/blueocean-plugin/blob/master/blueocean-rest/README.md#fetch-user-favorites