Python 2 running on Windows, causes thread leaks which
leads console io write errors when using pastel. This
works around the issue by limiting to a single worker
in these environments.

Fix and improve handling of extras while resolving dependencies

* Improve performance of package ordering/tagging after version solving has been completed

* Fix CI errors

Co-authored-by: Zack Weger <zackary.weger@aon.com>

* Display actual repository name in publish, not always PyPI

FreeBSD build environments cannot use `get-poetry.py` script as this
requires a release to be bootstrapped. These environments also do not
support Python 3.9 yet. This change ensures that non-linux
environments use `pip` to install poetry.

Resolves: #2815

Resolves: #2376

This change ensures that PEP 517 fallback builds are enabled by default
for when metadata inspection and setup.{py,cfg} parsing fails. This is
required in order to ensure that package requirements are correctly
identified for packages beyond first level dependencies.

Resolves: #2807

This change ensures that packages that only have a pre-release versions
are pragmatically discovered via `find_packages` when a constraint (*)
is specified.

Resolves: #2819

The existing example:
```bash
poetry export -f requirements.txt > requirements.txt
```
The problem with this is that any additional output from poetry will also end up in the requirements file. For instance, if the `poetry.lock` file is not present, poetry will output to stdout some extra text telling you about this. This breaks the requirements file. (I was burned by this problem, hence this PR)

Seeing as there is already a documented option to specify the filename directly, which resolves this issue, updating the docs like this seems reasonable.

* Add note for setting up poetry in a pre-existing project.

Resolves: #2630

* Show poetry init in more detail

* Update docs to reflect real poetry init usage

This change ensures that the executor does not deadlock on IO errors,
for example when IO does not support non-ascii characters.

Misc. clean up: Development dependencies, doc build action, tox for doc builds, pre-commit hook updates (#2814)

* docs: move build dependencies to tox environment

* provider: mark wheel as unsafe package

* Fix tox default configuration

* pre-commit: update hooks

* actions: add workflow for doc sanity build

* isort: update configuration to v5

* flake8: fix issues

* Update pyproject.md

Explain that `poetry install` installs the scripts in the virtualenv. See #2179 for the use case.

read package name from pypi info .info.name
close #2098

Resolves: #2333

Prior to this change, when checking solver results the tests cases
relied on the weaker equality check of the `Package` class. With
python-poetry/poetry-core#53, the check has been made stricter.

This change, while having no functional impact, ensures that once
poetry-core is updated, tests do not fail unexpectedly.

This works around a glob parsing bug in cirrus-ci.

Relates-to: cirruslabs/cirrus-ci-docs#696

Relax tomlkit version requirement

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