With this change, names containing "." are treated as namespace
packages.

The following behaviour is now expected.

- "a.b.c" creates package name "a-b-c" with directory structure
  "a/b/c"
- "a-b-c" creates package name "a-b-c" with directory structure
  "a/b/c"
- "a.b_c" creates package name "a-b-c" with directory structure
  "a/b_c"
- "a_b_c" creates package name "a-b-c" with directory structure
  "a_b_c"

- remove unnecessary template duplication
- stop generating default test case (this is out of scope for poetry)
- stop generating content for package `__init__.py`
- simplify inheritance to only require base directory overrides
- remove "StandardLayout" (replaced with `Layout`)
- support handling namespace package names given in the form "a.b.c"
- specify include packages by default (be explicit)

This change is in preparation for the removal of the old bootstrap
method in favour of the new `install-poetry` script. Releases no
longer require platform specific build artifacts.

This change replaces various cases in which installed distribution and
file look-ups used path searches with importlib.metadata backed
look-ups.

This fixes issues with `dist-info` lookup for PEP610 implementation as
well as `.pth` file look-up and `dist-info` removal.

* tests: add case for transitive markers propagation

Relates-to: #3878

* deps: update poetry-core

Relates-to: #3878

* env: ignore warnings when executing python scripts

When executing python scripts with an intent to deserialise via
`json.loads` we need to ensure we ignore warnings. This is required
because, warnings can cause a `JSONDecodeError`.

Resolves: #3897

* ci: use current source if experimental

text taken from https://github.com/python-poetry/poetry/releases/tag/1.1.5

* Used pyupgrade to remove compatibility code

May fix #3860

Resolves: #3842

discordapp.com domain will go defunct very soon, everything has transitioned to discord.com now

https://support.discord.com/hc/en-us/articles/360042987951-Discordapp-com-is-now-Discord-com

Replace updates of os.environ with explcit passing of `env` to
subprocess calls.

Relates-to: #3199