Merge cockroachdb#96379

96379: logictest: add mixed-version tenant bootstrap test case r=postamar a=postamar

This commit enhances the testserver_upgrade_node logic test suite with cases that verify that in a mixed-version cluster, tenant creation bootstraps the same data in the tenant span regardless of which executable is currently performing it. Until the upgrade is finalized, the executables for the new release must behave exactly like those for the old release.

Informs cockroachdb#94773.

Release note: None

Co-authored-by: Marius Posta <[email protected]>