[p3-cli] Complete tests for `environment::get_initial_cwd`

[saulecabrera]

At the time of writing, the current implementation in Wasmtime is incomplete, it returns None. We should update the tests once bytecodealliance/wasmtime#9831 lands.

[vados-cosmonic]

While the original PR didn't land, bytecodealliance/wasmtime#13468 did. An update for anyone working on this, we need to make sure this test is covered:

https://github.com/bytecodealliance/wasmtime/blob/main/crates/test-programs/src/bin/p2_cli_initial_cwd.rs