perf: buffer accumulation in _write_query_params() reduces f.write() calls

Replace the per-parameter write_value(f, param) loop in
_QueryMessage._write_query_params() with list.append + b"".join +
single f.write().  This reduces the number of write() syscall-like
calls from (2*N + 1) to 1 for N query parameters.

Benchmarks (500K iterations, best-of-5, Python 3.14, Cython .so):
  128D float32 vector (1 param):  1.25x faster
  768D float32 vector (1 param):  1.12x faster
  1536D float32 vector (1 param): 1.11x faster
  10 text columns:                1.30x faster

Also removes the unnecessary super() pass-through in
ExecuteMessage._write_query_params() to eliminate MRO lookup overhead.

Includes benchmark script and 14 new unit tests covering normal, NULL,
UNSET, mixed, empty, large vector, and many-parameter scenarios.

Author: mykaul