Add LocalClient for filesystem-based blobstore

[johha]

Implements a pure Ruby filesystem blobstore client as an alternative to fog-local. This provides a lightweight, dependency-free option for local development and testing environments.

Key changes:

• Add LocalClient and LocalBlob classes in lib/cloud_controller/blobstore/local/
• Update ClientProvider to support 'local' and 'local-temp-storage' blobstore types
• Add 'blobstore_type' configuration option to all config schemas (api, worker, clock, deployment_updater, blobstore_benchmarks)
• Update config/cloud_controller.yml to use local-temp-storage as default
• Add comprehensive specs for LocalClient and LocalBlob
• LocalClient matches fog-local behavior including parent directory cleanup

The LocalClient implementation:

• Stores blobs as files in a configurable directory
• Supports all standard blobstore operations (exists?, cp_to_blobstore, download_from_blobstore, delete, etc.)
• Automatically creates parent directories and cleans up empty ones on delete
• Uses consistent logging with 'blobstore.cp-start/finish/skip' prefixes
• Thread-safe file operations

Config parameters:

• blobstore_type: local or blobstore_type: local-temp-storage
• local_blobstore_path: Base directory (only for blobstore_type: local)

This enables simpler local development workflows without requiring S3-compatible blobstore or fog-local gem.

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• I have made this pull request to the main branch

• I have run all the unit tests using bundle exec rake

• I have run CF Acceptance Tests