resolves #9119

New Tests

Graph Tests (we will likely want these in 5.3 version of this, but not necessarily)

• [-] addRelatedRecords mutation dedupes
• [-] addRelatedRecords mutation asserts duplicates if we want it to
• replaceRelatedRecords mutation dedupes
• [-] replaceRelatedRecords mutation can assert duplicates if we want it to
• [-] test local graph mutation notification behaviors for addRelatedRecords, removeRelatedRecords, replaceRelatedRecords

Model/Main Tests

• ManyArray mutation dedupes for replace
• ManyArray mutation dedupes for splice in with adds
• ManyArray mutation dedupes for splice in with adds & removes
• ManyArray mutation dedupes for push
• ManyArray mutation dedupes for unshift
• ManyArray is not overly notified/churning on mutation
• ManyArray can optionally assert for duplicates