When building match result patterns the tuples they must qouted
with { }, which causes a problem with variable patterns.

Use element(1, Match) instead of trying to build the two tuple.

* dgud/mnesia/ext-backend/PR-858/OTP-13058:
  mnesia_ext: Add basic backend extension tests
  mnesia_ext: reuse snmp field for ext updates
  mnesia_ext: Create table/data containers from mnesia monitor not temporary processes
  mnesia_ext: Implement ext copies index
  mnesia_ext: Load table ext
  mnesia_ext: Dumper and schema changes
  mnesia_ext: Refactor mnesia_schema.erl
  mnesia_ext: Ext support in fragmented tables
  mnesia_ext: Backup handling
  mnesia_ext: Create schema functionality
  mnesia_ext: Add ext copies and db_fold to low level api
  mnesia_ext: Refactor record_validation code
  mnesia_ext: Add create_external and increase protocol version to monitor
  mnesia_ext: Add ext copies to records
  mnesia_ext: Add supervisor and behaviour modules

Minimal impact when talking to older nodes.

Tables or data containers should be owned and monitored by mnesia_monitor and
should thus be created by that process.

Always create_table before loading it

We need to create tables for ram_copies at least before loading
them as they are intermittent. It is also needed to get mnesia
monitor as the parent and supervisor of the data storage.

Make ram_copies index always use ordered_set

And use index type as prefered type not a implementation requirement,
the standard implmentation will currently ignore the prefered type.