Use importlib.metadata instead of reading pyproject.toml in init

[or150]

Hi,
This change makes pre-commit usages work again and fixes issues #249, #228.

The root cause for the issue is poetry-core just released a version 2.0 that doesn't add the pyproject.toml file to the root of site-packages, which I guess it wasn't there on purpose.

It uses importlib.metadata instead of reading pyproject.toml, which should be compatible with both versions of poetry-core.

Thought about also changing build-system to:

[build-system]
requires = ["poetry-core>=1.0.0,<3.0.0"]

WDYT?

[lokhman]

@hadialqattan I think this should possibly go sooner, as many would disable pycln, since there is no clear remedy for making it work with the new version of Poetry.

[hadialqattan]

@or150 Thanks a lot for the PR, I'll finalize it and do a release (right now).

CC: @lokhman

[hadialqattan]

Sorry for being late.

[codeclimate]

Code Climate has analyzed commit 298c9b4 and detected 0 issues on this pull request.

View more on Code Climate.

[hadialqattan]

@or150 @lokhman please use v2.5.0.