update env remove logic (#6195)

Resolves: #6018 

1. Added a check so that if `python` argument is a file (then it should
be a python path) - extract it's venv name and raise `IncorrectEnvError`
if it doesn't belong to this project
    **Before**
    ```
└❯ poetry env remove
~/.cache/pypoetry/virtualenvs/different-project-OKfJHH_5-py3.10/bin/python
    /bin/sh: 1: different-project-OKfJHH_5-py3.10: not found

Deleted virtualenv: ~/.cache/pypoetry/virtualenvs/poetry-4pWfmigs-py3.10
    ```
    Removes current project's env, which is wrong.
    **After**
    ```
└❯ poetry env remove
~/.cache/pypoetry/virtualenvs/different-project-OKfJHH_5-py3.10/bin/python

Env different-project-OKfJHH_5-py3.10 doesn't belong to this project.
    ```
2. Added the exact same check as before ^, but for cases where env name
is passed.
    **Before**
    ```
    └❯ poetry env remove different-project-OKfJHH_5-py3.10      
     /bin/sh: 1: different-project-OKfJHH_5-py3.10: not found

Command different-project-OKfJHH_5-py3.10 -c "import sys;
print('.'.join([str(s) for s in sys.version_info[:3]]))" errored with
the following return code 127, and output:
    ```
Errors while trying to exec env name as an interpreter, error is not
clear.
    **After**
    ```
└❯ poetry env remove different-project-OKfJHH_5-py3.10

Env different-project-OKfJHH_5-py3.10 doesn't belong to this project.
    ```
3. Added a couple of tests for **new** and for **old** scenarios which
weren't tested.
4. Added `venv_name` fixture for `tests/utils` directory to use in
`test_env`. Also replaced some of `"simple-project"` hardcoded value to
use `poetry.package.name`

It's up to maintainers to choose what they want for this project - I'm
happy either way if we at least fix the bug. I can remove/change any of
the stuff I added on top of the fix. But yeah I just decided that if we
fix the bug, we might also make some improvements/changes in this area
of code. Any thoughts on this are welcome, thanks!