Implements the reviews from #3987 and #3988. Special thanks to the
committers and reviewers there.

Co-authored-by: Harry Peach <harrypeach1999@gmail.com>
Co-authored-by: Kamyar Ghasemlou <kamyar@kamy.me>
Co-authored-by: Leonardo Freua <leonardo.batista.freua@gmail.com>

https://github.com/python-poetry/poetry-core/pull/245

In order to ensure coverage discovery and prevent flaky tooling.

For now we're thinking this generates too much noise -- we'll add it
back as we approach 3.11 RCs

After digging around in the poetry code to figure out
how to include an `extras` key in a CLI script,
I thought it might be a useful thing to add to the docs
for future users.

Export requirements.txt without index URLs

Co-authored-by: DBM012 <dustin.moriarty@amfam.com>

get() is a function and not an object with __enter__ (aka context manager)

When a project specifies a narrow range for the supported python
versions, i.e. "python ~= 3.6.1" and the current interpreter falls
outside of that range, the fallback code fails to test an available
python3.6 interpreter because of a too strict a test.

Relates to: #2153
When running `poetry update`, during the download phase when `PYTHONWARNINGS="default"` environment variable is set, multiple different sessions trigger resource warnings. This fixes one of them that occurs during the download phase of the package update.

```
/Users/username/Library/Application Support/pypoetry/venv/lib/python3.10/site-packages/poetry/installation/executor.py:594: ResourceWarning: unclosed <ssl.SSLSocket fd=5, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('REDACTED', 59025), raddr=('140.108.3.33', 80)>
```

This line references:
```
 593   │             try:
 594   │                 archive = self._download_archive(operation, link)
 595   │             except BaseException:
 596   │                 cache_directory = self._chef.get_cache_directory_for_link(link)
```

The issue is being caused because the session is being left open when the class is later cleaned up. By adding a destructor method, we can close the session if it exists, preventing this error.

test_env_shell_commands_with_stdinput_in_their_arg_work_as_expected contains path comparison which does not take into account potential symlinks.
When testing under MacOS and brew-installed python, venv version points to a path with symlink while python outputs the resolved path.

Co-authored-by: Arun Babu Neelicattu <arun.neelicattu@gmail.com>
Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

The `debug resolve` had an extra row included in its table, adding extra
whitespace. Also, remove a list that is discarded immediately.