Add more assertions for cluster(distribution) mode

**Is your feature request related to a problem? Please describe.**

In cluster mode, performing the Last join query without index optimization (enable_distsql=true) is not allowable. So, the engine should throw a compile error when we turn on enable_distsql instead of running with wrong results.

This issue is going to add more assertions in cluster mode to avoid bugs like #612

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Look at issue #612 for context on the bug. The work involves adding assertions in cluster mode, likely in the query compiler or planner when enable_distsql is true. Search for 'enable_distsql' and 'Last join' in the codebase to find relevant files. The goal is to throw a compile error instead of producing wrong results. Run existing tests related to cluster mode and distsql to ensure the new assertions work.

Scritto dal modello di indicizzazione a partire dal testo della issue.