Dolt doesn't respect the original order of CHECK, UNIQUE constraints in schemas

[zachmu]

We appear to output these in show create table statements in hash order or similar.

P0: output a consistent order across commits
P1: output the same order that was entered at table creation time

[druvv]

We previously were tracking the issue here:
#2673

[druvv]

I don't believe this is an issue with dolt. The customer was introspecting their postgres schema using the following query:

select tc.table_name, conname, string_agg(col.column_name, ',')
from (
        select conname, contype, unnest(conkey) as cols
        from pg_catalog.pg_constraint
        ) constr
join information_schema.table_constraints tc on constraint_name = conname
join (
        select table_name, table_schema, column_name, ordinal_position
        from information_schema.columns
        order by ordinal_position
    ) col
    on col.table_name = tc.table_name and col.table_schema = tc.table_schema and col.ordinal_position = cols
where contype = 'u'
group by tc.table_name, conname;

Testing this query out, I spun up a postgres 11 instance and created a table with a unique constraint:

> CREATE table t (pk int PRIMARY key, col1 int, col2 int, CONSTRAINT col1_col2_uq UNIQUE (col1, col2));
CREATE TABLE
> \d t;
                  Table "public.t"
 Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------
 pk     | integer |           | not null |
 col1   | integer |           |          |
 col2   | integer |           |          |
Indexes:
    "t_pkey" PRIMARY KEY, btree (pk)
    "col1_col2_uq" UNIQUE CONSTRAINT, btree (col1, col2)

Then I ran the above query:

> select tc.table_name, conname, string_agg(col.column_name, ',')
from (
        select conname, contype, unnest(conkey) as cols
        from pg_catalog.pg_constraint
        ) constr
join information_schema.table_constraints tc on constraint_name = conname
join (
        select table_name, table_schema, column_name, ordinal_position
        from information_schema.columns
        order by ordinal_position
    ) col
    on col.table_name = tc.table_name and col.table_schema = tc.table_schema and col.ordinal_position = cols
where contype = 'u'
group by tc.table_name, conname;
 table_name |   conname    | string_agg
------------+--------------+------------
 t          | col1_col2_uq | col2,col1

Notice how the string_agg column lists the column names in the wrong order.

Adding an order by clause in the string_agg seems to fix this problem:

> select tc.table_name, conname, string_agg(col.column_name, ',' order by col.ordinal_position)
from (
       select conname, contype, unnest(conkey) as cols
       from pg_catalog.pg_constraint
       ) constr
join information_schema.table_constraints tc on constraint_name = conname
join (
       select table_name, table_schema, column_name, ordinal_position
       from information_schema.columns
       order by ordinal_position
   ) col
   on col.table_name = tc.table_name and col.table_schema = tc.table_schema and col.ordinal_position = cols
where contype = 'u'
group by tc.table_name, conname;
table_name |   conname    | string_agg
------------+--------------+------------
t          | col1_col2_uq | col1,col2