Fix coglet wheel builds to install Pydantic dependency
When installing coglet wheels (embedded, pinned URL, or custom), Pydantic
was not explicitly installed, causing ModuleNotFoundError when user code
imports from pydantic. This change adds 'pydantic>=1.9,<3' to all coglet
wheel installation commands, consistent with how the cog wheel is installed.
Also skip test_build_with_complex_output for coglet-alpha since the pinned
version (v0.5.0-alpha18) doesn't support custom Pydantic BaseModel outputs.
