HHH-18835 fix of an AssertionError with InsertSelect using legacy naming strategy

[peter1123581321]

The related bug-ticket in Jira describes an AssertionError when using hibernate.id.db_structure_naming_strategy=legacy with an InsertSelect-query on MySQL.

The AssertionError occurs because the row number window function is used instead of the hibernate_sequence table.

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https://hibernate.atlassian.net/browse/HHH-18835

[beikov]

Thanks for the test and attempt to fix. Unfortunately the fix wasn't quite correct, because you can't use table sequences for insert-select directly. One must use the row numbering scheme and update the temporary table with generated values, but that only happens when using the multi-table insert strategy. I fixed the condition that was missing a case in the superseded PR: #11570