feat: redirect IPROTO_EXECUTE to sbroad SQL

Summary

• feat: redirect IPROTO_EXECUTE to sbroad SQL

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• Close #850 (closed), #980 (closed)
• Cherry-pick to: none
• Docs follow-up: not necessary
• See: #640 (closed), tarantool-module!551 (merged), picodata/tarantool#59
• Follow-ups: #941 (closed), sbroad#833 (moved), #1001, #1004 (closed)