Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/docs/idf/evidence/security-device-06/console.txt

@@ -0,0 +1,15 @@
+-- test_trust_domain_and_pool (free heap 112008, largest block 81920)
+-- test_signing_profiles (free heap 111700, largest block 81920)
+-- test_fail_closed (free heap 111700, largest block 81920)
+-- test_fail_closed: unknown issuer (free heap 111700, largest block 81920)
+-- test_fail_closed: expired ticket (free heap 111700, largest block 81920)
+-- test_fail_closed: SN-DECAP (free heap 111700, largest block 81920)
+-- test_identifier_change (free heap 111700, largest block 81920)
+-- test_gn_core_identifier_change (free heap 111700, largest block 81920)
+-- test_sf_facilities_hook (free heap 111700, largest block 81920)
+-- test_verification (free heap 111700, largest block 81920)
+-- verification cost: certificate-signed 34664 us (chain + message), digest-signed 34612 us (message only), ECDSA verify alone 29666 us
+-- test_ecies (free heap 111108, largest block 81920)
+-- test_enrolment_and_authorization (free heap 111108, largest block 81920)
+PASS: 668 checks (host/component tests, not ETSI ATS verdicts)
+VIDF_TEST_RESULT=0

microbu-esp32c5/external/vanetza-idf/docs/idf/evidence/security-device-06/result.json

@@ -0,0 +1,18 @@
+{
+  "kind": "component-tests",
+  "target": "esp32c5",
+  "idf_version": "6.0.2",
+  "port": "COM11",
+  "status": "pass",
+  "reset": "none",
+  "checks": 668,
+  "backend": "BackendMbedTls (PSA Crypto, mbedTLS 4.1.0 of ESP-IDF 6.0.2) with CONFIG_MBEDTLS_HARDWARE_ECDSA_VERIFY; 668 checks = 794 host checks minus the OpenSSL-only oracle tests",
+  "capture": "listen-only after the esptool post-flash reset",
+  "verifies": "receive-side verification (test_verification) on the device; verification cost line: digest-signed message 34.6 ms end to end, raw ECDSA P-256 verify 29.7 ms on the ECDSA peripheral (control build without the peripheral: 57.6 ms raw, 62 ms end to end, not retained)",
+  "sha256": {
+    "application": "2a14764ceb3062010f9d466b80a1a2dbd178611d52adf8dc479d5933d82e32a4",
+    "bootloader": "93903cefa2bae3f5805a604ae744fabfdea78a866a1230ec3cc129190b93fe40",
+    "partition_table": "73c0b5c3e5fcba3a151cc70c453c93dd5f4798899e7f2f8cca76da1f32ffc501",
+    "sdkconfig": "e793777a0f878c17d97d1a34de6c9a136b9239b52cb23d17874790951b4bd752"
+  }
+}