Allocate and track statement objects in pysqlite_statement_create.
By allocating and tracking creation of statement object in
pysqlite_statement_create(), the caller does not need to worry about GC
syncronization, and eliminates the possibility of getting a badly
created object. All related fault handling is moved to
pysqlite_statement_create().
Co-authored-by: Victor Stinner <vstinner@python.org>.
(cherry picked from commit fffa0f9)
Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@innova.no>