feat: support creating tiered sharded table via SQL

Summary

Added support of creating tiered sharded tables via SQL.

Added following checks on stage of creating DDL for sharded tables:

1. Check that specified tier present.
2. Check that at least one instance belongs to specified tier.

Tier membership information for sharded tables stored in distribution field in _pico_table system table.

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• Close #641 (closed)
• Cherry-pick to: none
• Docs follow-up: not necessary
• See also sbroad!428 (merged)