feat: find workspace root, for repos with several sub-workspaces

[DavidVujic]

…repos where the Workspace root is not the same as the git root

Description

Find the Workspace root for repos containing the Polylith workspace in a sub-directory, and when not using the workspace.toml to configure the workspace.

As before, when the workspace.toml cannot be located, the lookup will fallback to the pyproject.toml file.

With the changes in this Pull Request, it is no longer assumed that the Polylith Workspace root is the same as the repo root (i.e. the .git folder). This is the new feature, making it possible to structure a monorepo like:

the_repo/
    pyhon/
        the_polylith_workspace/
            bases/
            components/
            projects/
            ...
    kotlin/
    javascript/
    ...

Also, there's an extra check for configs in workspace.toml in case of an empty file with the contents moved to pyproject.toml.

Motivation and Context

fixes #295

How Has This Been Tested?

✅ CI
✅ Local install of CLI and the Poetry plugin: tested the example repos
✅ running commands in a repo with the Python Workspace(s) in a subfolder of the repo root.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have read the code of conduct.
• I have read the contributing guide.
• I have updated the documentation accordingly (if applicable).