Support running pytest under WASI

What's the problem this feature will solve?

I'm trying to run pytest under the WASI build of CPython, but pytest's extensive use of os.dup() prevents it from working.

If you're curious to reproduce:

1. Grab a WASI build from https://github.com/tiran/cpython-wasm-test/releases
2. Unpack it somewhere
3. From the same directory where you unpacked python.wasm: PIP_REQUIRE_VIRTUALENV=0 py -3.11 -m pip install --target . --only-binary=:all: --implementation=py --abi=none --abi=any pytest (if you don't have the Python Launcher, take out -3.11 and add the pip flag --python_version="3.11")
4. Try running wasmtime run --dir=. python.wasm -- -m pytest -h

It looks like:

https://github.com/pytest-dev/pytest/blob/03b19945fb000a82d0012b5720b05cf88c0973be/src/_pytest/capture.py#L381

is the first instance of os.dup() you run into, but even with --capture=no/s, you still run into:

https://github.com/pytest-dev/pytest/blob/61cfaacec695d91ab3b52477f780db4d441170a4/src/_pytest/faulthandler.py#L29

Describe the solution you'd like

I would love to be able to provide instructions to projects on how to run pytest under WASI to see if their project is compatible.

Alternative Solutions

Additional context

Reproduce the failure with the WASI CPython build and the provided wasmtime command. Read src/_pytest/capture.py around line 381 and src/_pytest/faulthandler.py around line 29, then determine the scope of WASI-compatible handling; done means pytest can run under WASI and projects have usable instructions.