clean up errors revealed by having a py.typed in poetry-core and running mypy in a proper environment

* more typechecking

* remove remaining `FooTypes` type annotations

just use the appropriate base class, no need for the extra complexity

* typecheck a couple more files

* more typechecking fixes

* more typechecking

* more typechecking

* tweak typing to appease pre-commit

* further mixology fixes

* consistency in repository package-finding

signal failure with `PackageNotFound`, rather than by returning None

* typechecking vcs.git.backend

updates:
- [github.com/pre-commit/mirrors-mypy: v0.942 → v0.950](https://github.com/pre-commit/mirrors-mypy/compare/v0.942...v0.950)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

This change introduces the config option
`experimental.system-git-client` defaulting to `false`. When set to
`true`, the subprocess git client implementation is used when cloning a
remote repository.

This option will be removed in a future release.

This change introduces dulwich as the git backend, instead of system
git executable. Together with an LRU cache when inspecting git package,
this considerable improves performance for dependency solver and reuse
of source when project has git dependencies.

In cases where dulwich fails with an HTTPUnauthorized error, Poetry
falls back to system provided git client as a temporary measure. This
will be replaced in the future once dulwich supports git credentials.

This change renames `safe_rmtree` into a more appropriate name with
relevant arguments. We ensure that the force behaviour is opt-in
and not the default to avoid ambiguity.

Relates-to: #5017

This ensures that `lock --no-update` does not change lockfile unnecessarily.

Consider all overwrites and not only the overwrites of one package when building the marker intersection

This ensures clean up is consistent.

This is done in order to avoid ambiguity between "default group" and "default dependencies" (the groups that are considered by a command by default)

This is no longer required and is superseded by the groups feature.

This change cleans up loading of plugins when testing commands.

This is done to allow safe refactoring of export command plugin.

This change ensures that content-hash generated by poetry < 1.2 does
not trigger unnecessary warnings and operations. We do this by using a
backwards compatible hashing logic.