`opentelemetry-instrumentation-dbapi`: capture `db.query.parameter.<key>`

Part of #4787 (global db.query.parameter.<key> tracking issue).

Background

dbapi is the shared base used by most SQL instrumentations (psycopg, psycopg2,
mysql, mysqlclient, pymysql, pymssql, sqlite3). Today CursorTracer._populate_span
captures parameters as a single non-standard db.statement.parameters blob when
capture_parameters=True, in all semconv modes and even on batch operations.

This sub-issue is foundational: it also adds the shared helper the other
sub-issues reuse.

What to do

1. Add a shared helper _set_db_query_parameters(result, parameters, sem_conv_opt_in_mode)
   in opentelemetry.instrumentation._semconv that:
   • only emits under the new database semconv (_report_new);
   • keys named parameters (mapping) by name and positional parameters
     (sequence) by 0-based index;
   • treats str/bytes as a single scalar (does not iterate characters);
   • stringifies each value, capturing falsy values too (0, False, "");
   • uses the DB_QUERY_PARAMETER_TEMPLATE constant from the semconv package
     (no hardcoded strings).
2. In CursorTracer._populate_span, when capture_parameters is enabled:
   • emit db.statement.parameters only under the old semconv (_report_old);
   • emit db.query.parameter.<key> under the new semconv via the helper;
   • skip db.query.parameter.<key> for batch operations (executemany),
     detected from the wrapped cursor method.

Acceptance criteria

• Default (old) semconv: db.statement.parameters unchanged; no
  db.query.parameter.*.
• database (stable) semconv: db.query.parameter.<key> emitted; no
  db.statement.parameters.
• database/dup semconv: both present.
• Positional params keyed by index, named params keyed by name, values are
  strings.
• executemany never emits db.query.parameter.*.

Tests

• Unit tests for the helper (positional, named, string-value type, scalar
  string, None, old-mode no-op).
• Integration tests in test_dbapi_integration.py for old / new / dup modes,
  named parameters and the batch-suppression case.

Start with the shared helper in opentelemetry.instrumentation._semconv and CursorTracer._populate_span, then read the semconv package constants and the existing tests. Run the helper unit tests and test_dbapi_integration.py for old, new, duplicate, named-parameter, and executemany cases. Done means the acceptance criteria hold across all semconv modes, including batch suppression.