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FLASHING.md says how to take a newer version of the colleague's tree (copy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-09/console.txt

@@ -0,0 +1,21 @@
+-- test_trust_domain_and_pool (free heap 107860, largest block 81920)
+-- test_signing_profiles (free heap 107592, largest block 81920)
+-- signing cost: SN-ENCAP 32350 us (digest signer), ECDSA P-256 sign alone 23223 us
+-- test_fail_closed (free heap 107592, largest block 81920)
+-- test_fail_closed: unknown issuer (free heap 107592, largest block 81920)
+-- test_fail_closed: expired ticket (free heap 107592, largest block 81920)
+-- test_fail_closed: SN-DECAP (free heap 107592, largest block 81920)
+-- test_identifier_change (free heap 107592, largest block 81920)
+-- test_gn_core_identifier_change (free heap 107592, largest block 81920)
+-- test_sf_facilities_hook (free heap 107592, largest block 81920)
+-- test_verification (free heap 107592, largest block 81920)
+-- verification cost: certificate-signed 36213 us (chain + message), digest-signed 35446 us (message only), ECDSA verify alone 29328 us
+-- test_chain_consistency (free heap 107592, largest block 81920)
+-- test_region_consistency (free heap 107364, largest block 45056)
+-- test_revocation (free heap 107120, largest block 34816)
+-- test_credentials (free heap 106980, largest block 34816)
+-- test_ecies (free heap 106392, largest block 34816)
+-- test_enrolment_and_authorization (free heap 106392, largest block 34816)
+-- test_trust_lists (free heap 106104, largest block 34816)
+PASS: 810 checks (host/component tests, not ETSI ATS verdicts)
+VIDF_TEST_RESULT=0

microbu-esp32c5/external/vanetza-idf/docs/idf/evidence/security-device-09/result.json

@@ -0,0 +1,14 @@
+{
+  "kind": "component-tests",
+  "target": "esp32c5",
+  "idf_version": "6.0.2",
+  "port": "COM11",
+  "status": "pass",
+  "reset": "none",
+  "checks": 810,
+  "backend": "BackendMbedTls (PSA Crypto, mbedTLS 4.1.0 of ESP-IDF 6.0.2) with CONFIG_MBEDTLS_HARDWARE_ECDSA_VERIFY, _ECC, _SHA, _MPI, _AES; 810 checks = 935 host checks minus the OpenSSL-only oracle tests",
+  "capture": "listen-only after the esptool post-flash reset",
+  "verifies": "as security-device-08 plus test_revocation (a revoked AA: REVOKED_CERTIFICATE, accepted again after withdrawal) and test_trust_lists (RCA CTL/CRL build, parse, apply); signing cost line: SN-ENCAP 32.4 ms, raw ECDSA P-256 sign 23.2 ms (software sign with the ECC point-multiplication accelerator); verification cost line: certificate-signed 36.2 ms, digest-signed 35.4 ms, raw verify 29.3 ms (ECDSA peripheral)",
+  "note": "the revocation scenario appended to test_chain_consistency failed on the device only: the sender's first signature after a receiver and three scoped stations had been created threw inside the PSA backend (statistics.failed = 1, an allocation failure with the heap fragmented); as its own test with a fresh heap it passes",
+  "sha256": "3986d2f2a862845d45235e96ee8f791f3a3edd59030ec9fa594930613e294424"
+}