feat: use Reflex UI for structured extract template (#209)

.changeset/lemon-houses-glow.md

.github/workflows/e2e.yml

e2e/basic.spec.ts

e2e/extractor_template.spec.ts

e2e/streaming_template.spec.ts

e2e/utils.ts

helpers/run-app.ts

index.ts

questions.ts

templates/components/engines/python/agent/engine.py

templates/components/engines/python/chat/engine.py

templates/components/vectordbs/python/llamacloud/__init__.py

templates/components/vectordbs/python/none/__init__.py

templates/types/extractor/fastapi/README-template.md

templates/types/extractor/fastapi/app/api/models.py

...ates/types/extractor/fastapi/app/api/routers/extractor.py

templates/types/extractor/fastapi/app/api/routers/main.py

templates/types/extractor/fastapi/app/app.py

templates/types/extractor/fastapi/app/config.py

templates/types/extractor/fastapi/app/engine/__init__.py