SqlViewMetricExporterSpi is redundant entity

SqlViewMetricExporterSpi is redundant entity both in terms of design and in terms of user experience.

METRICS SQL view is the internal entity that could exist regardless of any exporters configuration. So it should be created on indexing module initialization. Also from an user stand point it is strange to configure special exporter in order to get access to the METRICS view via SQL.

See also IGNITE-12921.