make \d table Collation field showing domains collation if that attribute is type of domain.

$subject related demos:
CREATE COLLATION case_insensitive (provider = icu, locale =
'@colStrength=secondary', deterministic = false);
create domain d_colli as text collate case_insensitive;
create domain d_collc as d_colli collate "C";
create table s1(a d_colli);
create table s2(a d_colli[] collate "C");
create table s3(a d_collc);

currently in HEAD:
\d s1
Table "public.s1"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
a | d_colli | | |

\d s2
Table "public.s2"
Column | Type | Collation | Nullable | Default
--------+-----------+-----------+----------+---------
a | d_colli[] | C | |

\d s3
Table "public.s3"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
a | d_collc | | |

we can change it to
\d s1
Table "public.s1"
Column | Type | Collation | Nullable | Default
--------+---------+------------------+----------+---------
a | d_colli | case_insensitive | |

\d s2
Table "public.s2"
Column | Type | Collation | Nullable | Default
--------+-----------+-----------+----------+---------
a | d_colli[] | C | |

\d s3
Table "public.s3"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
a | d_collc | C | |

as you can see:
For non-domain types, everything is the same as before.
but domains with COLLATION clauses behave differently.

main changes:
@@ -1866,7 +1866,7 @@ describeOneTableDetails(const char *schemaname,
attrdef_col = cols++;
attnotnull_col = cols++;
appendPQExpBufferStr(&buf, ",\n (SELECT c.collname
FROM pg_catalog.pg_collation c, pg_catalog.pg_type t\n"
- " WHERE
c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <>
t.typcollation) AS attcollation");
+ " WHERE
c.oid = a.attcollation AND t.oid = a.atttypid and c.collname <>
'default' ) AS attcollation");

it will make a table column with type "name", display Collation "C",
since "name" type typcollation is 'C',
other than this all behavior is the same as HEAD.

what do you think?