build: make the ODP real-change delta tests runnable

[jrosskopf]

odp/test/harness/run_delta_tests.sh was wired into nothing — not the Makefile, not
CI, not any script. grep -r run_delta_tests matches only the file itself.

That matters because it is the only delta coverage in the repo that proves anything.
Every delta test in odp/test/sql runs against 0D_FC_C01$F, a static fact cube
that never changes, so they can assert at most "a second call returns nothing". The
harness writes rows through a CDS view and asserts the actual values that come back —
VAL, REV, ODQ_CHANGEMODE — across insert, update, delete, mixed and bulk
scenarios.

Adds two targets:

make delta_fixtures_odp   # deploy the ABAP fixtures, once per fresh system
make delta_tests_odp      # run the real-change scenarios

Deliberately not folded into sql_tests_odp: the harness mutates the SAP system,
so it cannot run unattended beside the other suites on a shared trial.

Found while auditing the ODP suite for assertion rigour (see DataZooDE/erpl-odp#8,
which fixes 17 assertions that could not fail).

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}