Replace configurable NotesMigration with a stub implementation

Remove MutableNotesMigration, NotesMigration.Snapshot,
NotesMigrationState, and NoteDbMode. The only way to run tests is with
NoteDb enabled. (Tests passing GERRIT_NOTEDB in the environment or
gerrit.notedb as a system property will still continue to work; the
property is just ignored.)

The method bodies of NotesMigration now simply return constant values.
The next step will be to eliminate usages of these methods.

Change-Id: I808a7cc8b3dc4bedb072f3737c2df9758edbdea5
12 files changed
tree: 3cf55df4d6a20ad0f6d248691b4d6e77b2af5f3c
  1. java/
  2. javatests/