Introduce a setting schema_type

Introduce a setting schema_type for system.metric_log table with schema type. There are three allowed schemas: wide -- current schema, each metric/event in a separate column (most effective for reads of separate columns), transposed -- similar to system.asynchronous_metric_log, metrics/events are stored as rows, and the most interesting transposed_with_wide_view -- create underlying table with transposed schema, but also introduce a view with wide schema which translates queries to underlying table. In transposed_with_wide_view subsecond resolution for view is not supported, event_time_microseconds is just an alias for backward compatibility. #78412 (alesapin).