fix: accept prepare/binary kwargs in DictCursor.execute(..) (#10030)

psycopg.Connection.execute(query, params, *, prepare=None, binary=False)
delegates to its underlying cursor as
cur.execute(query, params, prepare=prepare). The DictCursor /
AsyncDictCursor in pgadmin.utils.driver.psycopg3.cursor narrowed the
signature to (self, query, params=None), so any caller that uses the
high-level Connection.execute() path with a cursor_factory=DictCursor
connection hits

    TypeError: execute() got an unexpected keyword argument 'prepare'

The most visible victim is psycopg_pool.ConnectionPool.check_connection,
which sends conn.execute("") to validate every checkout — every
connection then looks broken to the pool and getconn() times out.

Forward prepare and binary (keyword-only) to the underlying
psycopg.Cursor / psycopg.AsyncCursor. Defaults match psycopg's own,
so existing callers see no behavior change.

Adds a regression test asserting both classes expose the kwargs as
keyword-only parameters. The test docstring leads with psycopg.Cursor
substitutability (DictCursor is a Cursor subclass; both kwargs must be
accepted to remain substitutable) and notes that Connection.execute is
just the most visible failure path — it forwards prepare but handles
binary by setting cur.format instead of forwarding it.