solver: print more information about packages with source_type when solving fails to avoid weird messages like "Because myapp depends on both demo (1.2.3) and demo (1.2.3), version solving failed."

This change is required to allow for subdirectories.

Co-authored-by: Bartosz Sokorski <b.sokorski@gmail.com>
Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

Fixes #2355

This works around an issue with cleo's `Command.choice` implementation.
If the user does not make a selection then an AttributeError is raised.

This change ensures that the provider is less eager when merging
duplicate dependencies for a package. In particular, takes into
consideration source type, url and reference if available.

Use the version from poetry.core always, one implementation is enough

Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

Testing against newer versions will help us keep abreast of any upcoming
issues. The older versions can be added as partial matrix entries if
desirable, but I do not believe this to be necessary.

Also re-order mypy in the workflow so that type errors fail fast (before
tests are run).

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

Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

perf(solver): reduce the number of overrides by avoiding adding dummy dependencies if the project's python constraint does not allow any version compatible with the marker of the dependency

Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>