test_protocol_features.py:
- test_use_metadata_id_parsing: SCYLLA_USE_METADATA_ID parsed from SUPPORTED
- test_use_metadata_id_missing: use_metadata_id False when key absent
- test_use_metadata_id_startup_options: key present in STARTUP when negotiated
- test_use_metadata_id_not_in_startup_when_not_negotiated: absent otherwise

test_protocol.py:
- test_execute_message_skip_meta_flag: _SKIP_METADATA_FLAG (0x02) is written
- test_execute_message_scylla_metadata_id_v4: result_metadata_id written on
  v4 when use_metadata_id=True (Scylla extension)
- test_execute_message_scylla_metadata_id_none_writes_sentinel: extension
  active but result_metadata_id=None writes empty sentinel b'' (LWT / mixed
  cluster); frame layout preserved
- test_execute_message_v5_metadata_id_none_writes_sentinel: v5 with
  result_metadata_id=None writes empty sentinel instead of TypeError crash
- test_recv_results_prepared_scylla_extension_reads_metadata_id
- test_recv_results_prepared_no_extension_skips_metadata_id
- test_recv_results_metadata_changed_flag
- test_recv_results_metadata_no_metadata_flag_skips_metadata_id

test_response_future.py:
_set_result METADATA_CHANGED path:
- test_set_result_updates_metadata_when_metadata_changed
- test_set_result_does_not_update_metadata_when_metadata_id_absent
- test_set_result_warns_when_metadata_id_but_no_column_metadata

_query per-connection feature gating (5 scenarios):
- test_query_sets_skip_meta_with_scylla_extension
- test_query_no_skip_meta_without_extension
- test_query_no_skip_meta_when_prepared_statement_has_no_metadata_id
- test_query_sets_skip_meta_for_protocol_v5
- test_query_no_skip_meta_when_result_metadata_is_none (LWT guard)

The test used ps.result_metadata = [] (falsy), making has_result_metadata=False
the reason can_skip_meta was False — not the use_metadata_id=False guard that
the test claims to exercise.  A connection with use_metadata_id=True but empty
result_metadata would have passed the same assertions, giving false confidence.

Use truthy result_metadata so that use_metadata_id=False is the sole deciding
factor, which is what the docstring says the test is verifying.

… type

Issues addressed:
- test_repeat_orig_query_after_succesful_reprepare used result_metadata_id='foo'
  (str) where the real type from read_binary_string is always bytes.  Changed to
  b'foo' and added assertion that the value is actually stored on the prepared
  statement (previously, deleting the update lines would not break any test).

New tests:
- test_execute_after_prepare_updates_result_metadata_id: verifies that after a
  successful reprepare both result_metadata and result_metadata_id are updated
  on the prepared statement.
- test_execute_after_prepare_no_metadata_id_in_response: verifies that when the
  reprepare response carries no result_metadata_id (extension not active on the
  reprepare connection), the existing result_metadata_id is left unchanged.

…ag_skips_metadata_id

The previous assertion used 'not hasattr(...) or ... is None' which would pass
even if the code had a bug that explicitly set result_metadata_id = None instead
of leaving the attribute absent.

result_metadata_id is not a class attribute on ResultMessage, so the correct
assertion is 'assert not hasattr(msg, "result_metadata_id")'.

column_metadata IS a class attribute (= None), so its assertion is adjusted to
'assert msg.column_metadata is None'.

Before this PR, _SKIP_METADATA_FLAG was never written to the wire — the skip_meta
field existed on _QueryMessage but _write_query_params did not use it.  The PR
activates it for the first time for all protocol versions.

The new test pins the v5 wire encoding: skip_meta=True must produce a 4-byte
flags word of 0x00000003 (VALUES_FLAG | SKIP_METADATA_FLAG), alongside the
always-present result_metadata_id sentinel for v5.

…path

The existing test used column_metadata=[] (falsy empty list).  The warning
branch also triggers for None (attribute absent entirely), which has different
semantics — it indicates the field was never set rather than explicitly empty.

The new test ensures both falsy forms trigger the warning and update
result_metadata_id without touching result_metadata.