Add option to drop unique constraints inside SyncEngine.migratePrimaryKeys

[diatoming]

Summary

This PR add an option to allow user drop unique constraints when migrating with SyncEngine.migratePrimaryKeys.

Motivation

Current migrate method only convert primary key to UUID, unique constraints has not been dealt with.

Changes

• Added dropUniqueConstraints to SyncEngine.migratePrimaryKeys
• Added parseUniqueConstraintRange func in PrimaryKeyMigration

Testing

• Added uniqueConstraintsDrop in PrimaryKeyMigrationTests, test schema for column and table unique constraints