Python: Phase 2 client-side caching - server_assisted field and client_trackinginfo

[affonsov]

Summary

Adds server_assisted field to Python ClientSideCache config and client_trackinginfo() diagnostic command.

Issue link

This Pull Request is linked to issue: Implement client-side caching Phase 2: server-assisted invalidation via CLIENT TRACKING
Closes #5961

Features / Behaviour Changes

• server_assisted: bool = False field in ClientSideCache dataclass - enables server-assisted invalidation when True
• client_trackinginfo() on CoreCommands base class (async + sync) - available on both standalone and cluster clients
• client_trackinginfo(route=...) cluster override in cluster_commands.py for routing to specific nodes
• client_trackinginfo() in BaseBatch

Implementation

• cache.py: added server_assisted field to ClientSideCache dataclass
• config.py: serializes server_assisted to protobuf in _set_client_side_cache_in_request()
• core.py: client_trackinginfo() on CoreCommands base (no route) - routes to a single node, consistent with CLIENT INFO behavior
• cluster_commands.py: cluster override with optional route parameter - use AllNodes() to get tracking info from all cluster connections

Limitations

• server_assisted=True requires RESP3 protocol (enforced by glide-core)
• In cluster mode, the no-arg variant routes to a single random node; use the route parameter to query all nodes

Testing

• Unit test verifying server_assisted field defaults and construction
• Integration tests are in the glide-core PR Core: Phase 2 client-side caching - server-assisted invalidation via CLIENT TRACKING #5962

Checklist

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated.
• CHANGELOG.md and documentation files are updated.
• Linters have been run and Prettier has been run.
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.