feat: support depending on bzlmod deps that use rules_swift_package_manager

[luispadron]

Fixes #769

Adds support for a non-root bzlmod module B that uses rules_swift_package_manager to define it's Swift dependencies to be depended upon by another module A which also uses rules_swift_package_manager.

The main issues are:

• swift_deps_info and swift_package repositories are currently generated even for non-root modules where they likely have no use.

These should be dev dependencies, so they're only available to the root module and can't be declared more than once in the bzlmod graph. This requires declaring the extension as dev_dependency = True. We likely need to re-design how from_package is used and/or add a new api (ex: swift_dev_deps.from_package_extras(declare_swift_package = True)).

• swiftpkg_* repositories are declared even if they have already been declared by another bzlmod module.

We need to update our logic to support resolving dependencies declared in more than one bzlmod module. We should potentially match bzlmod resolution logic here and support single_version_overides in from_package.