all: rename to connection pool

[tsubakiky]

This pull request replaces the use of AsyncClientSession with AsyncConnectionPool across the codebase to improve connection handling. The most significant changes involve updating imports, constructor arguments, and method parameters to reflect this transition. Below is a categorized summary of the key changes:

Core Refactor: Transition to AsyncConnectionPool

• Replaced imports of AsyncClientSession with AsyncConnectionPool in various files, including generator.go, client_runner.py, and service_connect.py. [1] [2] [3]
• Updated constructors for client classes (e.g., ConformanceServiceClient and ElizaServiceClient) to accept a pool parameter instead of session. [1] [2] [3] [4]
• Modified function arguments and documentation to reflect the use of AsyncConnectionPool for managing connections. [1] [2]

Updates to Client Logic

• Adjusted client logic to utilize AsyncConnectionPool in place of AsyncClientSession for making requests, including in the handle_message function and client initialization. [1] [2] [3]
• Updated protocol-related classes (e.g., ProtocolClientParams) to include a pool parameter instead of session. [1] [2]

New Connection Pool Module

• Introduced a new module, connection_pool.py, which provides the AsyncConnectionPool functionality using httpcore.

These changes ensure a more efficient and scalable approach to managing HTTP connections by leveraging connection pooling.