Add PuLID VRAM leak reproduction tests

[huchenlei]

https://github.com/Mikubill/sd-webui-controlnet/issues/2862

This PR adds tests on detect endpoint on PuLID and generation with PuLID.

To run test:

• Open task manager to monitor VRAM usage
• Make sure an SDXL model is selected
• Install test dependencies by executing pip install -r requirements-test.txt under webui directory
• Under webui directory, execute python -m pytest --junitxml=test/results.xml --cov .\extensions\sd-webui-controlnet\ --cov-report=xml --verify-base-url .\extensions\sd-webui-controlnet\tests\web_api\generation_test.py::test_pulid to run generation test.

Observation: You can observe that vram generally kept stable after 6 runs with different ref images.

[JIAOJIAYUASD]

When I use Pulid with the new version of controlnet, I also get a OOM after 9 reference images change. My controlnet version is v1.1.448.