Mitigates: #3134

This change drops support for Python 2.7 and 3.5 in tox, ci and release
workflows in preparation for dropping support for these versions in
Poetry 1.2.0.

(cherry picked from commit ed43d94b423a7bf53dfb530a549b686d016ab891)

(cherry picked from commit 733736cd1c2ea6189a77e34ab640059dbff2be23)

Previously, when determining nested dependencies, the check for
activated extras/features of top level dependencies were done after the
nested dependencies were processed. This lead to exports containing
in active extras. This change resolves this by pre-selecting top level
packages prior to identifying nested dependencies.

(cherry picked from commit 2b6f82e9494b99bdb04d0dac90f87eb23548e4a5)

(cherry picked from commit a7d66767a089c5604803a0a2d96ddc5fcb41c043)

(cherry picked from commit b29450c19034cf34856cf6e2a610507411833e36)

This change ensures that markers are propagated from top level
dependencies to the deepest level by walking top to bottom instead of
iterating over all available packages.

In addition, we also compress any dependencies with the same name and
constraint to provide a more concise representation.

Resolves: #3112 #3160
(cherry picked from commit e78a67ba139c70ee1856834711ddaf14de0c926a)

Resolves: #3115
(cherry picked from commit 04967db7ab20558b593e6b47ef5258e95a1b642f)

This change, moves common functionality from exporter into the locker
to allow for sharing of logic that can generate `DependencyPackage`
instances given a a list of requirements using the lock data.

(cherry picked from commit c2adb3283c0b76e290a8f25053bf035500b47cb2)

Resolves: #3116
(cherry picked from commit 50e06289a40819afe68f9b9cfecd7ccf08763476)

Resolves: #3129
(cherry picked from commit 38fddf05b36ec64647e66bf459578f9e0b41442d)

Resolves: #3069

Relates-to: #3155

Closes #3144

Resolves: #2754

This change ensures that package inspection will handle rich core
metadata available for poetry managed projects. This will allow, nested
local path dependencies to use "develop" mode packages.

Resolves: #3098

Resolves: #2658 #3086

Resolves: #3022

This change ensures that we resolve dependencies to correctly propagate
markers when using `lock --no-update`.

Resolves: #3048

Resolves: #3073

This change ensures that we create closer to reality scenarios when
testing init command.

Relates-to: #3073

Resolves: #3065

Resolves: #3054

Resolves: #3045

Relates-to: #3028

Resolves: #3018

Fixes #3026

If the context wrapped by the temporary_directory() context manager
raised ImportError (for example because distutils.util cannot be
imported, #721 #1837), it would previously keep going, causing a
RuntimeError from contextlib:

    RuntimeError: generator didn't stop after throw()