v0.12.0

• add Linux ARMv8 (aarch64) native binary library
• add obx_sync_* APIs (actual functionality is only available in a sync-enabled version; see https://objectbox.io/sync/)
• add obx_has_feature(), and OBXFeature enum: please use these instead of the following, now deprecated functions:
  obx_supports_bytes_array(), obx_supports_time_series(), and obx_sync_available()
• add obx_remove_db_files() to delete database files in a given directory
• add optional OBXEntityFlags_SHARED_GLOBAL_IDS for SYNC_ENABLED entities
• semi-internal: add custom async callback APIs for Dart/Flutter language binding