Restore replication settings when modifying a field type

When the user modifies the REPLICA IDENTIFY field type, the logical
replication settings are lost.

For example:

postgres=# \d+ t1
Table "public.t1"
Column | Type | Collation | Nullable | Default | Storage | Stats
target | Description
--------+---------+-----------+----------+---------+---------+--------------+-------------
col1 | integer | | | | plain |
|
col2 | integer | | not null | | plain |
|
Indexes:
"t1_col2_key" UNIQUE CONSTRAINT, btree (col2) REPLICA IDENTITY

postgres=# alter table t1 alter col2 type smallint;
ALTER TABLE
postgres=# \d+ t1
Table "public.t1"
Column | Type | Collation | Nullable | Default | Storage | Stats
target | Description
--------+----------+-----------+----------+---------+---------+--------------+-------------
col1 | integer | | | | plain |
|
col2 | smallint | | not null | | plain |
|
Indexes:
"t1_col2_key" UNIQUE CONSTRAINT, btree (col2)

In fact, the replication property of the table has not been modified,
and it is still 'i'(REPLICA_IDENTITY_INDEX). But the previously
specified index property 'indisreplident' is set to false because of the
rebuild.

So I developed a patch. If the user modifies the field type. The
associated index is REPLICA IDENTITY. Rebuild and restore replication
settings.

Regards,
Quan Zongliang