fix(D012_01_exc, D015_01_exc): complete the § 9.3.3 exclusive-pinning sweep (also un-leaks D001)

The exclusive-mode batch tests were restructured to satisfy TS 104-175 § 9.3.3 (exclusive registrations pin specific entity ids; an exclusive claim must not overlap an Attribute the broker stores locally): D013/D014/D016 use entity_id= + entity_id2= with the two-group fixture context-source-registration-vehicle-speed-with-batch-ops-exclusive. D012_01_exc and D015_01_exc were missed — their registrations still used entity_id_pattern=urn:ngsi-ld:Vehicle:* and got 400, and D015's local twins carried the claimed 'speed' attribute, earning a 409.

With setup failing, teardown crashed on unset suite variables and the two local=true setup entities leaked into every later unpinned type=Vehicle query: D001_01_inc / D001_02_inc / D001_03_03_inc fail with 'Lengths are different: 1 != 5' in full-suite runs.

Same recipe as the sweep: pinned ids + the exclusive fixture, and D015's local twins move to vehicle-simple-attributes-second.jsonld (no 'speed'). The entity_id2= keyword support and the exclusive fixture are re-declared identically to their origin branch (unmerged MR) — git deduplicates on merge.

Analysis recorded as testsuite-doubts.md #95.