Add project.json migrator

[nkolev92]

Bug

Related: NuGet/Home#7199
Fixes: https://github.com/NuGet/Client.Engineering/issues/3158

Description

As part of the project.json migration, we need to expose the migrator in the references node of the migrator. This will allow us to prompt migration for customers.

Note that the migrator already exists and has been used for UWP project.json migration.

In addition to exposing the migrator, I have also added a migration event that will allow us to track the status of the migration.

https://github.com/NuGet/Client.Engineering/issues/3158

It has the following properties:

Property	Description
ProjectId	Allows us to correlate to the project information events.
ProjectFullPath	Allows us to correlate to the restore events
Status	The status of the operation. We're looking for success, we'd dig deeper if we get any failures
Status	Performance purposes.
StartTime	Performance purposes.
EndTime	Performance purposes.

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests Unfortunately there's no tests for the context menus. I'll ask the test team to add test cases for this.
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc. - Document the project.json migrator Home#14071

[jgonz120]

lgtm!