Consolidate TMGimporter integration tests into one file

Merge test_integration_libtmg.py into test_integration.py — shared helpers
(_Rec, _table, _make_db, _add_person) are deduplicated at the top, and
the E2E RELPH-pipeline class now sits alongside the 12 DB-backed
function-level test classes (117 tests total).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: eduralph