Ensure Ai usage events have namespace_path filled

Summary

We support namespace_path for code suggestions on DB level, however we don't send this information from our IDE extensions nor we process it on our backend. We need this information to proprely link merge requests to specific code suggestion usages.

Proposal

1. Send project_id\namespace_id from IDE extensions where possible with each code suggestions usage metric (out of scope of this issue)
2. Store in in ClickHouse namespace_path field.