work with hypopg coredump

[HUST-Huyajun]

create extension hypopg ;
load 'pg_hint_plan';

create table t1(a int, b int, c int);
create index ON t1 (a);

select hypopg_create_index('create index on t1(b)');
explain select/*+ indexscan(t1 t1_a_idx)*/ from t1 where a = 3 and b =4 ;
-- coredump

it seems like pg_hint_plan does not consider the impact of hypothetical indexes, restrict_indexes should filter out the hypothetical IndexOptInfo in RelOptInfo