fix: panic on non-unique index name

Summary

• fix: panic on non-unique index name

• we didn't check that index name is unique in indexes meta table. That led to panics when index with same name was created for two tables.
• previous commit set wrong sbroad submodule. Set sbroad submodule to correct commit

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• Close #611 (closed)
• Changes should be cherry-picked to 24.2: no
• Docs follow-up: not necessary