DRIVERS-2884 Avoid connection churn when operations timeout

[prestonvasquez]

This PR implements the design for connection pooling improvements described in DRIVERS-2884, based on the CSOT (Client-Side Operation Timeout) spec. It addresses connection churn caused by network timeouts during operations, especially in environments with low client-side timeouts and high latency.

When a connection is checked out after a network timeout, the driver now attempts to resume and complete reading any pending server response (instead of closing and discarding the connection). This may require multiple checkouts.
Each pending response read is subject to a cumulative 3-second static timeout. The timeout is refreshed after each successful read, acknowledging that progress is being made. If no data is read and the timeout is exceeded, the connection is closed.

To reduce unnecessary latency, if the timeout has expired while the connection was idle in the pool, a non-blocking single-byte read is performed; if no data is available, the connection is closed immediately.
This update introduces new CMAP events and logging messages (PendingResponseStarted, PendingResponseSucceeded, PendingResponseFailed) to improve observability of this path.

Please complete the following before merging:

• Update changelog.
• Make sure there are generated JSON files from the YAML test files.
• Test changes in at least one language driver. Go: GODRIVER-3173 Complete pending reads on conn checkout mongo-go-driver#1977
• Test these changes against all server versions and topologies (including standalone, replica set, sharded
  clusters, and serverless).

[baileympearson]

CMAP changes look good to me. Pending Shane's second implementation though.

[isabelatkinson]

Are drivers without CSOT (currently Rust and C) expected to implement these changes in their retryability behavior as part of this ticket? If so, I think we should add retryability-only tests in this PR or prioritize DRIVERS-3216.

[prestonvasquez]

@isabelatkinson I think this update would only be relevant to driver that implement CSOT. Otherwise, the only I/O that occurs during checkout is the connection handshake which have tests prescribed in DRIVERS-746.

For context, this ticket introduces I/O to CMAP to both "drain" the TCP buffer and perform aliveness checks for connections pending response data. The pathological case is the aliveness check which will return an error but preserve the connection if successful and so should retry at the operation layer.

[isabelatkinson]

retryability spec changes LGTM. Rust does not have CSOT, so I'm not able to POC/test