Download devfile stack extra files during component initialization

[vrubezhny]

Add functionality to download additional stack files (Dockerfile, Kubernetes manifests, etc.) when creating components from devfile registry sources. This brings odoInit to feature parity with the real odo CLI.

Key Changes:

• Add DevfileRegistry.downloadStackExtraFiles() API for downloading stack files referenced in devfile components (dockerfile.uri, kubernetes.uri)
• Download files directly from GitHub devfile registry repository via HTTPS (no ORAS/OCI dependencies needed)
• Implement two-level caching: in-memory (ExecutionContext) + filesystem (~/.local/state/vs-openshift-tools/devfile-registry-cache/)
• Integrate into odoInit to download files after devfile resolution
• Add 5 comprehensive integration tests covering all scenarios

Implementation Details:

• Files are downloaded from: https://raw.githubusercontent.com/devfile/registry/main/stacks/{name}/{version}/{uri}
• Cache location follows XDG Base Directory spec on Linux/macOS and is cross-platform compatible with Windows
• Downloads are optional and don't fail init if files are unavailable
• Language-agnostic solution works for all stacks (Go, Python, Java, etc.)

Testing:

• Integration tests verify: basic download, caching, multiple files, error handling, and devfiles without extra files
• All cross-platform path operations use Node.js standard APIs (path.join, os.homedir, os.tmpdir)

Fixes the issue where components created with odoInit were missing deployment-related files that real odo init creates.

Assisted-By: Claude Sonnet 4.5 noreply@anthropic.com

[codecov]

Codecov Report

❌ Patch coverage is 81.39535% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.29%. Comparing base (da60441) to head (eed7b87).
⚠️ Report is 1862 commits behind head on main.

Files with missing lines	Patch %	Lines
src/devfile-registry/devfileRegistryWrapper.ts	88.73%	8 Missing ⚠️
src/devfile/init.ts	46.66%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5942       +/-   ##
===========================================
+ Coverage   32.37%   49.29%   +16.92%     
===========================================
  Files          85      110       +25     
  Lines        6505    10011     +3506     
  Branches     1349     2241      +892     
===========================================
+ Hits         2106     4935     +2829     
- Misses       4399     5073      +674     
- Partials        0        3        +3     

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