Python: Isolate openrewrite package by version and add recipeInstallDir

[knutwannheden]

Summary

• Resolves a version-specific subdirectory under pipPackagesPath (e.g., <basePath>/0.5.3/) so different openrewrite package versions don't overwrite each other. Two CLI versions shipping the same openrewrite package version share the directory — no duplication.
• Adds recipeInstallDir(Path) to PythonRewriteRpc.Builder for a separate shared directory containing user-installed recipe packages (added to PYTHONPATH alongside the version-specific openrewrite directory). Mirrors recipeInstallDir on the JavaScript RPC builder.

Context

When multiple Moderne CLI versions share ~/.moderne/cli, they conflict over the openrewrite Python package — one version can break another. Currently both the openrewrite package (bootstrapped by the RPC) and user-installed recipe packages live in a single shared directory.

After this change, the layout becomes:

~/.moderne/cli/python/openrewrite/<package-version>/
  rewrite/                    ← version-specific
~/.moderne/cli/recipes/pip/
  rewrite_recipe_example/     ← shared across CLI versions

Test plan

• Verify existing Python recipe tests still pass
• Verify bootstrapOpenrewrite installs into the version-specific subdirectory
• Verify recipeInstallDir is added to PYTHONPATH when set