TST: Add tests for SELECT updates

Summary

Tests for caosdb-pylib#48 (closed). Ensure that updates of SELECT results can't be conducted. Two of three are still marked as xfail Until caosdb-pylib#48 (closed) and caosdb-server#155 have been resolved

Focus

Tests in tests/test_select.py

Test Environment

Ensure that the test runs through. Maybe remove the xfails to see that these two will fail atm.

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