feat: add stricter API contract for runtime base

[hallvictoria]

• Add package name getter method for runtime base
• RuntimeBase class now enforces the same API contract as the V2 runtime, requiring all extending runtime classes to implement:

Event Handlers (async):

• worker_init_request
• functions_metadata_request
• function_load_request
• invocation_request
• function_environment_reload_request

Threadpool Management:

• start_threadpool_executor
• stop_threadpool_executor
• get_threadpool_executor

Context Tracking:

• invocation_id_cv property

Version

• version.VERSION