Add Undici fuzzing integration

[rootvector2]

This adds an initial OSS-Fuzz integration for Undici, the HTTP client used by Node.js.

The integration uses the JavaScript/Jazzer.js OSS-Fuzz setup and adds three fuzz targets covering:

• Headers, Request, and Response construction and header mutation
• undici.request with a MockAgent, so fuzzing does not make network calls
• fetch with FormData and a mocked response path

A couple of notes about the setup:

• The project is pinned to Undici's v6.x branch for now. Current Undici releases require a newer Node.js runtime than the OSS-Fuzz JavaScript base image provides.
• Jazzer.js is rebuilt inside the image because the published Linux prebuild currently requires a newer glibc than the OSS-Fuzz base image has. The rebuild is pinned to the same Jazzer.js version installed by npm.
• primary_contact is set to [email protected], matching the existing Node.js OSS-Fuzz project contact.

I verified this locally with:

DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py build_image --no-pull undici
DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py build_fuzzers --clean --engine libfuzzer --sanitizer none undici
DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py check_build --engine libfuzzer --sanitizer none undici
DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py run_fuzzer --engine libfuzzer --sanitizer none undici fuzz_headers -- -runs=25
DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py run_fuzzer --engine libfuzzer --sanitizer none undici fuzz_request -- -runs=25
DOCKER_DEFAULT_PLATFORM=linux/amd64 python3 infra/helper.py run_fuzzer --engine libfuzzer --sanitizer none undici fuzz_fetch_formdata -- -runs=25

[rootvector2]

I also opened an upstream Undici issue asking maintainers to confirm the OSS-Fuzz contact and leave an LGTM if the integration looks good from their side: nodejs/undici#5154

[github-actions]

rootvector2 is integrating a new project:
- Main repo: https://github.com/nodejs/undici.git
- Criticality score: 0.65204