BREAKING CHANGES: Most metrics have been prefixed with Prometheus subsystem names to avoid conflicts between different collection methods.

• [BUGFIX] Separate slave_status and global_status into separate subsystems.
• [IMPROVEMENT] Refactor metrics creation.
• [IMPROVEMENT] Add support for performance_schema.table_io_waits_summary_by_table collection.
• [IMPROVEMENT] Add support for performance_schema.table_io_waits_summary_by_index_usage collection.
• [IMPROVEMENT] Add support for performance_schema.events_statements_summary_by_digest collection.
• [IMPROVEMENT] Add support for Percona userstats output collection.
• [IMPROVEMENT] Add support for auto_increment column metrics collection.
• [IMPROVEMENT] Add support for SHOW GLOBAL VARIABLES metrics collection.