fix: inject version for path dependencies in workspace virtual manifests

[tomkarw]

There was an unhandled case in version injection task.

For a project with virtual manifest like this:

# in /Cargo.toml

[workspace.dependencies]
subcrate = { path = "./subcrate" }

Kraken would not inject version and registry attributes.

This MR fixes it, by correctly injecting versions for dependencies declared in workspaces with virtual manifest.

Decisions:

• Add _raw attribute to most manifest related classes, store raw JSON data there (without removing the handled fields)
• For fields that already had a subset of this, rename the field to _raw and use a getter with deprecation warning for backward compatibility
• All to_json methods could be simplified, as they can simply return self._raw

[NiklasRosenstein]

LGTM overall; would be nice to have a test that checks if the version gets injected correctly into the workspace dependencies!