The error message at Cluster.add_execution_profile() had an unfilled %s
placeholder: 'Failed to create all new connection pools in the %ss timeout.'
The pool_wait_timeout value was never interpolated into the string, so
users would see a literal '%s' instead of the actual timeout value.

Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>

Improve timeout observability in the driver, inspired by the Go driver
PR scylladb/gocql#847.

OperationTimedOut now carries optional timeout and in_flight fields that
are appended to the exception message when present (e.g.
"(timeout=10.0s, in_flight=42)"). All seven production raise sites in
connection.py and cluster.py pass these values where available.

Additionally, debug-level log lines are emitted for:
- Client-side request timeouts (host, timeout, in_flight, orphaned)
- Server-side read/write timeouts (host, consistency, received/required,
  data_retrieved/write_type, retry decision)

A helper _retry_decision_name() translates RetryPolicy constants to
human-readable strings for the log messages.

New keyword-only parameters are backward compatible — existing callers
that pass only positional errors/last_host continue to work unchanged.

Fixes: DRIVER-538

Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>