New "My Items" plugin needed

[akhenry]

Is your feature request related to a problem? Please describe.
The "my items" object currently depends on a mixture of code that is split between the legacy and current APIs. The legacy code should be replaced, and the code consolidated into a new "My Items" plugin.

Describe the solution you'd like
The legacy "My Items" bundle should be removed, and replaced with a "My Items" plugin (Under src/plugins/MyItems). The legacy My Items bundle did two things, one of which has already been replaced with new code:

1. It creates a "My Items" root object. This can be replaced with a call to openmct.objects.addRoot('mine')
2. It creates a "My Items" model. This has already been replaced by an "Object Interceptor" that does the same thing using the current API, however the interceptor code should be moved into the new "My Items" plugin.

The new My Items plugin will need to be exposed on the openmct API object so that it can be easily installed.

[jvigliotta]

Testing

• verify "My Items" folder is showing up correctly
• if possible, delete "My Items" (DO NOT DELETE on Banner \ try on local couchDb) from the DB or start a new instance of Open MCT where "My Items" is not in the DB and verify it does show up

[nikhilmandlik]

Tested locally with coucdb, after deleting mine from couchdb on UI my items shows up but there is no corresponding document in couchdb.