PG16: Fix flaky test

In PG16 new collations named `en_US` and `en-US` on Windows bootstrap
that are incompatible with UTF-8. So added the `collencoding` to the
order of the query that determine the collation name to get another
compatible collation.

tsl/test/expected/compressed_collation.out

@@ -5,9 +5,9 @@
 -- We have different collation names such as en_US, en-US-x-icu and so on,
 -- that are available on different platforms.
 select * from (
-    select 3 priority, 'en_US' "COLLATION"
-    union all (select 2, collname from pg_collation where collname ilike 'en_us%' order by collname limit 1)
-    union all (select 1, collname from pg_collation where collname ilike 'en_us_utf%8%' order by collname limit 1)
+    select 3 priority, 'C' "COLLATION"
+    union all (select 2, collname from pg_collation where collname ilike 'en_us%' order by collencoding, collname limit 1)
+    union all (select 1, collname from pg_collation where collname ilike 'en_us_utf%8%' order by collencoding, collname limit 1)
 ) c
 order by priority limit 1 \gset
 create table compressed_collation_ht(time timestamp, name text collate :"COLLATION",

tsl/test/sql/compressed_collation.sql

@@ -7,9 +7,9 @@
 -- We have different collation names such as en_US, en-US-x-icu and so on,
 -- that are available on different platforms.
 select * from (
-    select 3 priority, 'en_US' "COLLATION"
-    union all (select 2, collname from pg_collation where collname ilike 'en_us%' order by collname limit 1)
-    union all (select 1, collname from pg_collation where collname ilike 'en_us_utf%8%' order by collname limit 1)
+    select 3 priority, 'C' "COLLATION"
+    union all (select 2, collname from pg_collation where collname ilike 'en_us%' order by collencoding, collname limit 1)
+    union all (select 1, collname from pg_collation where collname ilike 'en_us_utf%8%' order by collencoding, collname limit 1)
 ) c
 order by priority limit 1 \gset